Organic semiconductor material and preparation method and application thereof

Abstract

The invention relates to the technical field of manufacturing of organic semiconductor materials, in particular to an organic semiconductor material which is reasonable in process, simple and convenient to prepare and capable of remarkably improving hole injection capacity, improving molecular arrangement and accumulation at an interface and further improving the performance of an OLED (Organic Light Emitting Diode) device when being applied to a hole transport material, and a preparation method and application of the organic semiconductor material. The chemical formula of the organic semiconductor material is # imgabs0 #. According to the invention, a substituent group with strong polarity is connected to the D-A alternating conjugated polymer in a side chain form, so that the dissolving capacity of the polymer is improved, an energy level matched with ITO is obtained, the arrangement and accumulation among polymer molecules are improved, and the performance of a multi-layer OLED device is further improved.

Description

Technical Field:

[0001] The present invention relates to the technical field of organic semiconductor material manufacturing, and specifically to an organic semiconductor material, a preparation method thereof, and an application thereof, which have a reasonable process, are easy to prepare, can significantly improve the hole injection ability and improve the molecular arrangement and packing at the interface when applied as a hole transport material, thereby improving the performance of OLED devices. Background Art:

[0002] Organic semiconductor materials have outstanding advantages that inorganic semiconductor materials do not have, such as light weight, printability, foldability, etc. They can also adjust optical properties such as optical band gap and absorption spectrum, and electrical properties such as conductivity and carrier mobility through the regulation of molecular structure. Supercapacitors, organic field effect transistors (OFETs), organic light emitting diodes (OLEDs), and perovskite solar cells (PSCs) prepared from them have great development and application prospects in the fields of flexible sensing, detection, and energy storage.

[0003] Among them, conjugated polymer organic semiconductor materials have high thermal stability and good environmental adaptability, and are more suitable for preparing polymer light emitting diodes by low-cost solution processing technologies such as laser thermal transfer and inkjet printing, and have great potential in large-area flexible display products. OLEDs are multi-layer structures composed of an anode, a hole transport layer (HTL), a light emitting layer (EML), an electron transport layer (ETL), and a cathode. The matching of the preparation, energy level, and film layer flatness among these structures plays a key role in improving the device performance. An excellent hole transport material can reduce the energy barrier with ITO, improve the hole injection efficiency, and balance the hole transport rate and the electron transport rate, so as to effectively recombine in the light emitting layer and improve the efficiency, lifetime, and brightness of the device. The alternating arrangement of donors and acceptors in alternating conjugated polymers can effectively promote charge transfer, and has significant advantages as a hole transport material. Its synthesis and development have been the main research direction in recent years. Polyethylenedioxythiophene as a donor and fluorene as an acceptor can synthesize typical alternating conjugated polymers. Although there have been reports of synthesizing high-yield materials at temperatures below 100°C by the direct alkylation method, the introduced alkyl side chains only provide single solubility, and the energy level of the polymer does not match well with that of ITO, resulting in its inability to be used as a hole transport material in OLED devices. Currently, the research on sulfonic acid groups mainly focuses on luminescent materials. For example, sodium polyvinyl sulfonate is used as a complexing agent to improve the solubility of poly(3,4-ethylenedioxythiophene). And sodium methoxybutanesulfonate side chains are made into SPEDOT to improve the charge transport efficiency of the heterocyclic main chain. As a polyelectrolyte group, sulfonic acid groups are widely used in electrochemical processes such as thickeners and dispersants. However, there is no report on using sulfonic acid groups as side chains of alternating conjugated polymers to improve the hole transport performance of polymers. Summary of the Invention:

[0004] In view of the drawbacks and deficiencies in the prior art, the present invention provides an organic semiconductor material, a preparation method thereof, and an application thereof. The organic semiconductor material has a reasonable process, is easy to prepare, can significantly improve the hole injection ability and improve the molecular arrangement and packing at the interface when applied as a hole transport material, thereby enhancing the performance of OLED devices.

[0005] The present invention is achieved by the following measures:

[0006] An organic semiconductor material, characterized in that the chemical formula of the organic semiconductor material is:

[0007]

[0008] The present invention also provides a preparation method of the above-mentioned organic semiconductor material, characterized in that the synthesis process of the organic semiconductor material is as follows:

[0009]

[0010] Among them, process i is the synthesis of 2,7-dibromo-9,9-bis(4-sodium butylsulfonate)fluorene, i.e., compound 2, which specifically includes the following steps:

[0011] Dissolve 2,7-dibromofluorene and tetrabutylammonium bromide in 50% sodium hydroxide aqueous solution and dimethyl sulfoxide (DMSO) respectively. Under a nitrogen atmosphere, drop the DMSO solution of 1,4-butanesultone into the mixed solution, stir at room temperature, precipitate the reaction solution with acetone to obtain a crude product, wash with ethanol and filter by suction, recrystallize twice with acetone / water, and dry at 60 °C for 24 hours to obtain compound 2.

[0012] Process ii is the synthesis of poly(3,4-ethylenedioxythiophene-2,5-diyl-alt-9,9-di-(4-sodium butylsulfonate)fluorene-2,7-diyl), i.e., the synthesis of compound PEF-2BSO3Na, which specifically includes the following steps:

[0013] In a two-necked flask, successively add compound 2 and 3,4-ethylenedioxythiophene (EDOT, 0.167 ml, 1.57 mmol) according to a molar ratio of 1:1, then add a base (potassium acetate) in a molar ratio of 1-3, deoxygenate the flask, then add anhydrous N,N-dimethylacetamide, deoxygenate the mixed solution, add 0.01-0.1 equivalent of precatalyst palladium(II) acetate (Pd(OAc)2), deoxygenate the flask again, heat the mixed solution to 80 °C under argon (Ar) and react for 24-72 hours, cool and pour into ether, filter by suction under vacuum, and use a Soxhlet extractor to wash away impurities with n-hexane, petroleum ether, dichloromethane, and methanol solvents, monitor the polymer components in the solvent, and finally perform low-pressure rotary evaporation and vacuum drying to obtain PEF-2BSO3Na.

[0014] The present invention also provides a PLED device, which is characterized in that the above-mentioned PEF-2BSO3Na is used as the hole transport layer. The PLED device includes a glass substrate with an indium tin oxide (ITO) coating. A super yellow toluene solution is spin-coated on the surface of the glass substrate with the indium tin oxide ITO coating, and then a Ca layer and an Al layer are sequentially evaporated and deposited. The thickness of the Ca layer is 40 nm, and the thickness of the Al layer is 60 nm.

[0015] The PLED device of the present invention is prepared by the following steps: First, the glass substrate with an indium tin oxide (ITO) coating is ultrasonically cleaned with deionized water, acetone and isopropyl alcohol, and then treated with oxygen plasma for 10 minutes. Before spin-coating, all solutions are magnetically stirred at 55 °C for 12 hours; on a clean ITO glass plate, a 1 mg / ml P2 hydrochloric acid solution (PH4) is spin-coated at a speed of 2000 rpm for 60 s, and a 5 mg / ml super yellow toluene solution is spin-coated at 1400 rpm for 60 seconds; finally, Ca and Al are evaporated and deposited.

[0016] By using a strongly polar substituent group in the present invention, which is connected to the D-A alternating conjugate polymer in the form of a side chain, while improving the solubility of the polymer, energy levels matching with ITO are obtained, the arrangement and packing between polymer molecules are improved, and thus the performance of the multi-layer OLED device is enhanced. Description of the Drawings:

[0017] Attached Figure 1 is the 1H NMR spectrum (400 Hz) of the PEF-2BSO 3 Na material in CDCl3. Detailed Embodiments:

[0018] The following further describes the present invention with reference to the drawings and embodiments.

[0019] In the present application, a sodium butyl-1-sulfonate side chain with multifunctional integration is introduced into the alternating conjugate polymer, aiming to improve the performance of the polymer material in the following three aspects: 1. The sulfonate group is soluble in polar solvents such as water. Compared with non-polar solvents, there are many polar solvents, which are more environmentally friendly and can also be used alternately with existing non-polar solvents to avoid corrosion of the previous layer. 2. The strong polarity of the sulfonate group makes the polymer molecular chains show obvious ordered arrangements, which can flatten the hole transport material after film formation and is beneficial to improving the performance of the device. 3. Since sodium butyl sulfonate is used and butyl serves as a transition chain, it will not affect the alternating electron transport ability of the main chain, so the high performance of the alternating conjugate polymer can be ensured.

[0020] Examples:

[0021] This example provides an organic semiconductor material, its preparation method and application. The monomer synthesis and direct arylation polycondensation scheme of the polymer in this example are as follows:

[0022]

[0023] Among them, synthesis process i is the synthesis of 2,7-dibromo-9,9-bis(sodium 4-butylsulfonate)fluorene, i.e., compound 2, which specifically includes the following steps:

[0024] Dissolve 2,7-dibromofluorene (4 g, 12 mmol) and tetrabutylammonium bromide (80 mg) in 50% sodium hydroxide aqueous solution (8 mL) and dimethyl sulfoxide (DMSO) (60 mL) respectively; under a nitrogen atmosphere, dropwise add a DMSO (20 mL) solution of 1,4-butanesultone (4 g, 29 mmol) to the mixed solution; stir at room temperature for 4 hours, precipitate the reaction solution with acetone to obtain a crude product, wash it with ethanol and filter it by suction, recrystallize it twice with acetone / water, and dry it at 60 °C for 24 hours to obtain compound 2;

[0025] Synthesis process ii specifically includes the following steps, i.e., the synthesis of poly(3,4-ethylenedioxythiophene-2,5-diyl-alt-9,9-di-(sodium 4-butylsulfonate)fluorene-2,7-diyl) (compound PEF-2BSO 3 Na):

[0026] In a 250 ml two-necked flask, add compound 2 (1 g, 1.57 mmol) and EDOT (0.167 ml, 1.57 mmol) in sequence according to 1:1 equivalent (the equivalent in this example is the molar ratio). Add 1 - 3 equivalents of potassium acetate, deoxygenate the flask, then add anhydrous N,N-dimethylacetamide (12 ml), deoxygenate the mixed solution, add 0.01 - 0.1 equivalent of precatalyst palladium(II) acetate (Pd(OAc) 2 ), and deoxygenate the flask again. The mixed solution is heated to 80 °C under argon (Ar) and reacted for 24 - 72 hours (to be optimized). After cooling, pour it into 100 ml of ether, filter it by vacuum, and use a Soxhlet extractor to wash away impurities with solvents such as n-hexane, petroleum ether, dichloromethane, and methanol, monitor the polymer components in the solvent, and finally perform low-pressure rotary evaporation and vacuum drying to obtain PEF-2BSO 3 Na.

[0027] The material properties obtained in this example are shown in the following table:

[0028] Table 1 Properties of the synthesized polymer

[0029]

[0030] As can be seen from the above table, the value of its highest molecular occupied orbital HOMO is -5 eV, which is close to the value of ITO (-4.7 eV) and lower than that of the EDOT-fluorene alternating polymer with dioctyl as the fluorene side chain (-5.41 eV), making it more suitable for matching with ITO. The maximum absorption peak of its infrared spectrum only differs by 3 nm under solution and film-forming conditions, indicating that the arrangement of molecules in polar solvents is very similar to that in the solid film state after solvent evaporation.

[0031] This example further provides a PLED device structure based on PEF-2BSO 3 with Na as the hole transport layer, which is ITO / PEF-2BSO 3 Na / super yellow / Ca(40 nm) / Al(60 nm). First, the glass substrate with an indium tin oxide (ITO) coating is ultrasonically cleaned with deionized water, acetone, and isopropyl alcohol, and then treated with oxygen plasma for 10 minutes. Before spin coating, all solutions are magnetically stirred at 55 °C for 12 hours. On a clean ITO glass plate, a 1 mg / ml P2 hydrochloric acid solution (PH4) is spin-coated at a speed of 2000 rpm for 60 s, and a 5 mg / ml super yellow toluene solution is spin-coated at 1400 rpm for 60 seconds. Finally, Ca and Al are deposited by evaporation. The PLED device is tested using a Keithley 4200 analysis system, and the obtained performance is shown in Table 2.

[0032] Table 2 Luminescence properties of PLEDs.

[0033]

[0034] In the present invention, by using strongly polar substituents and connecting them to the D-A alternating conjugate polymer in the form of side chains, while improving the solubility of the polymer, energy levels matching with ITO are obtained, the arrangement and packing between polymer molecules are improved, and thus the performance of multi-layer OLED devices is enhanced.

Claims

1. An organic semiconductor material, characterized in that The chemical formula of organic semiconductor materials is:

2. A method for preparing an organic semiconductor material as claimed in claim 1, characterized in that: The synthesis process of organic semiconductor materials is shown as follows: Among them, process i is the synthesis of 2,7-dibromo-9,9-di(sodium 4-butylsulfonate)fluorene, i.e. compound 2, which specifically includes the following steps: 2,7-dibromofluorene and tetrabutylammonium bromide were dissolved in 50% sodium hydroxide aqueous solution and dimethyl sulfoxide (DMSO) respectively. Under nitrogen environment, 1,4-butane sultone (DMSO) solution was added dropwise to the mixed solution and stirred at room temperature. The reaction solution was precipitated into a crude product with acetone, washed with ethanol and filtered, recrystallized twice with acetone / water, and dried at 60°C for 24 hours to obtain compound 2. Process ii is the synthesis of poly(3,4-ethylenedioxythiophene-2,5-diyl-alt-9,9-di-(sodium 4-butylsulfonate)fluorene-2,7-diyl), that is, the synthesis of the compound PEF-2BSO3Na, which specifically includes the following steps: In a double-necked flask, compound 2,3,4-ethylenedioxythiophene EDOT is added in sequence according to a 1:1 molar ratio, and then a base is added, potassium acetate or potassium carbonate is used as the base to deoxygenate the flask, and then anhydrous N,N-dimethylacetamide is added to deoxygenate the mixed solution, and 0.01 to 0.1 equivalents of precatalyst palladium acetate (II) (Pd(OAc)2) is added, and the flask is deoxygenated again. The mixed solution is heated to 80°C under argon and reacted for 24 to 72 hours. After cooling, ether is poured into it, vacuum filtered, and impurities are washed away with n-hexane, petroleum ether, dichloromethane, and methanol solvents using a Soxhlet extractor, and the polymer component in the solvent is monitored. Finally, low-pressure rotary evaporation and vacuum drying are performed to obtain PEF-2BSO3Na.

3. A PLED device, characterized in that: The PEF-2BSO3Na as described above is used as a hole transport layer. The PLED device includes a glass substrate with an indium tin oxide (ITO) coating. Super yellow toluene solution is spin-coated on the surface of the glass substrate with the indium tin oxide (ITO) coating, and then a Ca layer and an Al layer are sequentially evaporated and deposited, wherein the Ca layer has a thickness of 40 nm and the Al layer has a thickness of 60 nm.

4. A PLED device as claimed in claim 3 is prepared by the following steps: first, a glass substrate with an indium tin oxide (ITO) coating is ultrasonically cleaned with deionized water, acetone and isopropanol, and then treated with oxygen plasma for 10 minutes; before spin coating, all solutions are magnetically stirred at 55°C for 12 hours; on a clean ITO glass plate, 1 mg / ml P2 hydrochloric acid solution is spin coated at a speed of 2000 rpm for 60 seconds, and 5 mg / ml super yellow toluene solution is spin coated at 1400 rpm for 60 seconds; finally, Ca and Al are evaporated and deposited.

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