Azobenzene-based cross-linked polyionic liquid ultraviolet photoelectric conversion material and preparation method and application thereof

Abstract

The application belongs to the technical field of semiconductor materials, and provides a cross-linked polyionic liquid ultraviolet photoelectric conversion material based on azobenzene and a preparation method and application thereof.The material is polymerized from an azobenzene photosensitive unit and an ionic liquid dipole unit; the ionic liquid dipole unit is a trimer structure as a cross-linking core, and ionic liquid dipole monomers are grafted at the ends of the structure. The ultraviolet photoelectric device made of the material greatly increases the resistance of the device to mechanical stress (such as bending and pressure) and improves the dimensional stability on the premise of maintaining electrical properties.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor materials, and relates to a photoelectric conversion material, in particular to a cross-linked polyionic liquid ultraviolet photoelectric conversion material based on azobenzene and a preparation method and application thereof. BACKGROUND

[0002] The photoelectric conversion polymer material based on a photosensitive unit is a material capable of converting a light signal into an electric signal. The photoelectric conversion polymer material based on a photosensitive unit reported at present is of a linear structure, and a preparation method is to introduce an azobenzene photosensitive unit and an ionic liquid dipole unit into a same polymer main chain. Under ultraviolet light irradiation, the azobenzene unit undergoes cis-trans isomerization, induces endogenous force, and transmits the force to the ionic liquid unit through a polymer chain, so that the positive and negative charge centers are separated, and thus an electric signal can be generated. The polymer is dissolved in a good solvent to configure a 0.05 g / mol polymer solution. Then, the polymer solution is spin-coated on a PET transparent electrode with a deposited Ni-Cu alloy on a surface, and is placed in an oven for vacuum drying until a constant weight. Then, a same material PET transparent electrode is attached to the other side of the polymer, and is pressed at room temperature for 5 min under a pressure of 10 kN to ensure that the polyionic liquid is in full contact with the electrode. Finally, after a copper wire is led out, a dimethylsiloxane (PDMS) encapsulation treatment is performed to obtain an ultraviolet photoelectric device. The core part of the device is composed of three layers, from top to bottom, namely, the Ni-Cu alloy, the polymer (polyionic liquid), and the Ni-Cu alloy.

[0003] The above method can obtain the photoelectric conversion polymer material based on the photosensitive unit, but still has many problems: (1) the polymer with a linear structure has poor mechanical firmness, mechanical stress resistance, size stability and high temperature resistance. (2) the azobenzene unit structure is single, and is all 4,4'-dihydroxyethyl azobenzene. The structure has a hard and brittle characteristic due to a short carbon chain of a substituent, and is prone to cracking under external force. (3) the photoelectric device containing only a single-layer polymer has unstable performance, and is prone to short circuit (two layers of the Ni-Cu alloy are separated by the polymer, and once the polymer is damaged and cracks, the two layers of the alloy are connected). SUMMARY

[0004] In view of the above problems existing in the prior art, one of the purposes of the application is to provide a cross-linked polyionic liquid ultraviolet photoelectric conversion material and a preparation method thereof. The mechanical stability of the photoelectric conversion material is improved by introducing a cross-linked structure.

[0005] The second purpose of the application is to provide an application of the cross-linked polyionic liquid ultraviolet photoelectric conversion material based on azobenzene in preparation of a photoelectric device.

[0006] To achieve the above-mentioned purposes of the application, the following technical solutions are adopted in the application:

[0007] The application provides a cross-linked polyionic liquid ultraviolet photoelectric conversion material based on azobenzene.

[0008] The structure formula of the ionic liquid dipole unit is as follows:

[0009] ;

[0010] R is an ionic liquid dipole monomer group.

[0011] In the technical scheme of the cross-linked polyionic liquid ultraviolet photoelectric conversion material, the azobenzene photosensitive unit is obtained by polymerization of azobenzene monomers and isocyanate.

[0012] Further, the isocyanate is one of hexamethylene diisocyanate, dicyclohexylmethane diisocyanate (HMDI), diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), and isophorone diisocyanate (IPDI).

[0013] Further, the azobenzene monomer is obtained by reaction of 4,4'-dihydroxyazobenzene and a heteroalkane containing an ether bond, and the type and length of the substituent group can be selected as required.

[0014] Further, the heteroalkane containing an ether bond is of a linear type or a non-linear type, and the number of ether bonds of the heteroalkane can be selected according to actual conditions.

[0015] Further, the azobenzene photosensitive monomer is preferably 4,4'-bis[2-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)ethoxy]azobenzene.

[0016] In the technical scheme of the cross-linked polyionic liquid ultraviolet photoelectric conversion material, the ionic liquid dipole monomer group meets the function of a piezoelectric unit when used, and the type of the ionic liquid dipole monomer group can be selected according to the type of the azobenzene unit used in actual use, and at least one of an imidazole ionic liquid group and a quaternary ammonium salt ionic liquid group is preferably used.

[0017] Further, the structure formula of the ionic liquid dipole unit is as follows:

[0018] .

[0019] The application also provides a preparation method of the cross-linked polyionic liquid ultraviolet photoelectric conversion material.

[0020] Preparation of azobenzene photosensitive unit;

[0021] Preparation of ionic liquid dipole unit;

[0022] Reaction of azobenzene photosensitive unit and ionic liquid dipole unit at 55-65℃ to obtain azobenzene-based cross-linked polyionic liquid ultraviolet photoelectric conversion material.

[0023] In a feasible implementation, the preparation steps of the azobenzene photosensitive unit are as follows:

[0024] Dissolve 4,4'-dihydroxyazobenzene, 2-(2-(2-(2-(bromoethoxy)ethoxy)ethoxy)ethanol, carbonate and iodide in a first organic solvent, react at 75-85℃ for 12-14h, and then extract, wash and dry the crude product obtained by reaction to obtain the target product 4,4'-bis[2-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)ethoxy]azobenzene monomer in deep red paste;

[0025] Mix 4,4'-bis[2-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)ethoxy]azobenzene monomer and isocyanate, react at 25-30℃ for 1-1.5h, and then react at 75-85℃ for 2-4h to obtain the azobenzene photosensitive unit.

[0026] In a feasible implementation, the molar ratio of 4,4'-dihydroxyazobenzene, 2-(2-(2-(2-(bromoethoxy)ethoxy)ethoxy)ethanol, carbonate and iodide is 10:(20-21):20:1; the molar ratio of 4,4'-bis[2-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)ethoxy]azobenzene monomer and hexamethylene diisocyanate is 1:2. The first organic solvent is dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMAC) or the like; the carbonate has no special requirements other than being able to absorb hydrogen bromide generated after the reaction, and the type of carbonate can be selected as needed in actual use, and the preferred carbonate is potassium carbonate or sodium carbonate; the iodide has no special requirements other than being able to catalyze the reaction, and the type of iodide can be selected as needed in actual use, and the preferred iodide is potassium iodide or sodium iodide.

[0027] In a feasible implementation, the preparation method of the ionic liquid dipole unit comprises:

[0028] The diethanolamine is added into the second organic solvent, stirred uniformly at 55-65℃, then the n-butyl bromide is added, and then heated and stirred at reflux at 85-95℃ for 45-55h, and the second organic solvent and unreacted n-butyl bromide are removed by rotary evaporation to obtain the quaternary ammonium salt-Br ionic liquid.

[0029] The quaternary ammonium salt-Br ionic liquid is mixed with 1-ethyl-3-methyl imidazoline bis(trifluoromethylsulfonyl) imide in a third organic solvent, and stirred at 25-30℃ for 20-30h, and then refrigerated at 0-5℃ for 18-25h; and then the third organic solvent is removed by rotary evaporation to obtain the quaternary ammonium salt-bis(trifluoromethylsulfonyl) imide ionic liquid monomer.

[0030] The quaternary ammonium salt-bis(trifluoromethylsulfonyl) imide ionic liquid monomer and the diisocyanate trimer are first reacted at 25-30℃ for 1-1.5h, and then reacted at 75-85℃ for 2-4h to obtain the ionic liquid dipole unit.

[0031] In a feasible preparation mode, the molar ratio of the diethanolamine, the n-butyl bromide, and the 1-ethyl-3-methyl imidazoline bis(trifluoromethylsulfonyl) imide is 1:(2-2.2):1; the molar ratio of the quaternary ammonium salt-bis(trifluoromethylsulfonyl) imide ionic liquid monomer and the diisocyanate trimer is 3:1; the diisocyanate trimer is one of hexamethylene diisocyanate trimer, toluene diisocyanate trimer, and isophorone diisocyanate trimer; the second organic solvent and the third organic solvent are good solvents for the solvent substances, and can be the same solvent or different solvents, and the preferred second organic solvent and the third organic solvent are both acetonitrile.

[0032] In a feasible implementation mode, the azobenzene photosensitive unit is reacted with the ionic liquid dipole unit at 55-65℃ for 0.5-1h to obtain a mixed solution containing a photoelectric conversion material, so as to facilitate subsequent operations such as re-dissolution and coating for device preparation. When the reaction time is greater than 1h, the reaction can be completely carried out, and a solidified photoelectric conversion material can be directly obtained. After the material is solidified, it cannot be re-dissolved and a device cannot be prepared by coating.

[0033] In practical applications, the types and amounts of the first organic solvent, the second organic solvent, and the third organic solvent are determined according to the types and amounts of the solute substances used, and meet the actual needs. The amount of the first organic solvent is such that the final concentration of 4,4'-dihydroxyazobenzene is 0.25mol / L~0.45mol / L, the amount of the second organic solvent is such that the final concentration of diethanolamine is 0.3mol / L~0.5mol / L, and the amount of the third organic solvent is such that the final concentration of 1-ethyl-3-methyl imidazoline bis(trifluoromethylsulfonyl) imide is 0.3mol / L~0.5mol / L.

[0034] Based on the cross-linked polyionic liquid ultraviolet photoelectric conversion material described above, the application also provides application of the cross-linked polyionic liquid ultraviolet photoelectric conversion material based on azobenzene in preparation of photoelectric devices.

[0035] The cross-linked polyionic liquid ultraviolet photoelectric conversion material is solidified between two electrode sheets to obtain a photoelectric device, and the specific steps are as follows:

[0036] The azobenzene photosensitive unit and the ionic liquid dipole unit are reacted at a molar ratio of 3:2 at 55-65℃ for 0.5-1h, then the obtained cross-linked polyionic liquid ultraviolet photoelectric conversion material based on azobenzene is uniformly coated on two electrode sheets respectively, and then solidified at 75-85℃ until the weight is constant; then the two electrode sheets coated with the cross-linked polyionic liquid ultraviolet photoelectric conversion material based on azobenzene are attached, and after pressing and packaging, the cross-linked polyionic liquid ultraviolet photoelectric device based on azobenzene is obtained. The thickness of the electrode sheet is 7-8μm, and the thickness of the coated photoelectric conversion material is 15-20μm.

[0037] Compared with the prior art, the application has the following beneficial effects:

[0038] 1) The polyionic liquid ultraviolet photoelectric conversion material provided by the application is a cross-linked material, and the trimer structure contained in the ionic liquid dipole unit is used as the cross-linking core, and then a cross-linked structure is formed after polymerization. The cross-linked polyionic liquid ultraviolet photoelectric conversion material has excellent mechanical firmness and mechanical stress resistance, thereby improving the dimensional stability and long-term durability of the material; and the high temperature resistance is also better than that of the linear photoelectric conversion material.

[0039] 2) The azobenzene photosensitive unit with a large number of ether bonds is used in the application, the structure of the azobenzene unit is enriched by adjusting the types, lengths and number of ether bonds, and the toughness and flexibility of the azobenzene unit structure are improved, and the cracking phenomenon under external force is reduced.

[0040] 3) The cross-linked polyionic liquid ultraviolet photoelectric device based on azobenzene provided by the application adopts a double-layer cross-linked polyionic liquid ultraviolet photoelectric conversion material in the middle, which greatly increases the resistance to mechanical stress (such as bending and pressure) of the device under the premise of maintaining electrical properties, and improves the dimensional stability; at the same time, the four-layer structure also improves the durability of the device. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 The photoelectric device prepared in Example 2; wherein (a) corresponds to an electrode sheet coated with a cross-linked polyionic liquid ultraviolet photoelectric conversion material (C-AZ-IL), (b) corresponds to an electrode sheet with a double-layer C-AZ-IL, and (c) corresponds to a C-AZ-IL ultraviolet photoelectric device with a four-layer structure.

[0042] Figure 2 Open circuit voltage test results of the photoelectric devices prepared for Example 2, Comparative Example 2 and Comparative Example 3.

[0043] Figure 3 Pictures of the photoelectric device prepared for Example 2 after mechanical test and high temperature test; where (a) corresponds to the initial state of the photoelectric device, (b) corresponds to the state after 30 times of bending and twisting, (c) corresponds to the state after 30 times of bending and twisting and then placed in an oven at 100°C for 2h.

[0044] Figure 4 Open circuit voltage test results of the photoelectric devices in three different states. Figure 3 DETAILED DESCRIPTION

[0045] The following examples are given to further illustrate the present application. It is necessary to point out that the following examples should not be construed as limiting the scope of the present application. If some non-essential improvements and adjustments are made to the present application by those skilled in the art according to the above content of the present application, they still belong to the protection scope of the present application.

[0046] Example 1

[0047] The present example provides a cross-linked polyionic liquid based on azobenzene UV photoelectric conversion material (C-AZ-IL), and the specific steps of the preparation method are as follows:

[0048] (1) Preparation of azobenzene photosensitive unit (prepolymer 1)

[0049]

[0050] In a 100 mL single-neck flask, 2.14 g (10 mmol) of 4,4'-dihydroxyazobenzene, 5.27 g (20.5 mmol) of 2-(2-(2-(2-(bromoethoxy)ethoxy)ethoxy)ethanol, 2.76 g (20 mmol) of anhydrous potassium carbonate, 0.166 g (1 mmol) of potassium iodide and 30 mL of dehydrated N,N-dimethylformamide (DMF) were sequentially added, and then reacted at 80°C for 13 h. After the reaction was completed, the crude product obtained by the reaction was dissolved in 500 mL of deionized water, and dichloromethane was added to extract the product. After the extract was washed with deionized water three times, the aqueous phase was collected and the solvent was removed by rotary evaporation at 80°C, and then the product was dried in vacuum at 85°C, to obtain the target product 4,4'-bis[2-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)ethoxy]azobenzene monomer (AZ) (5.11 g, 68.9% yield) in the form of a dark red paste.

[0051] ​Take 20 g (0.0359 mol) of 4,4'-bis[2-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)ethoxy]azobenzene monomer (AZ), 12.08 g (0.0718 mol) of hexamethylene diisocyanate (HDI) in a 250 mL three-necked flask, respectively at 30°C for 1.5 h and at 80°C for 3 h, and the obtained prepolymer 1 is the azobenzene photosensitive unit, which is packaged in a brown glass bottle.

[0052]

[0053] (2) Preparation of ionic liquid dipole unit (prepolymer 2)

[0054]

[0055] Take 10.514 g (0.10 mol) of diethanolamine (colorless transparent viscous liquid) into a 500 mL single-necked flask, then add 250 mL of acetonitrile and stir uniformly at 60°C until there is no layering. Use a syringe to measure 28.56 g (0.21 mol) of n-butyl bromide and inject it into the single-necked flask, and stir at reflux at 90°C for 50 h to obtain a transparent solution. Then remove the acetonitrile at 80°C by rotary evaporation, and then remove the residual n-butyl bromide at 110°C by rotary evaporation to obtain a slightly yellow transparent viscous fluid, which is the quaternary ammonium salt-Br ionic liquid.

[0056] Add 39.1 g (0.1 mol) of 1-ethyl-3-methylimidazoline bis(trifluoromethylsulfonyl) imide to the quaternary ammonium salt-Br ionic liquid obtained in the previous step, and then add 250 mL of acetonitrile, and stir at 30°C for 25 h to cause anion exchange reaction, obtaining a light yellow solution. Then place it in a 2°C refrigerator for 25 h to ensure that the anion exchange reaction occurs completely. Take the solution out of the refrigerator, and remove the acetonitrile at 80°C by rotary evaporation to obtain the quaternary ammonium salt-bis(trifluoromethylsulfonyl) imide ionic liquid monomer (IL). In addition, 1-ethyl-3-methylimidazole bromide is not removed and remains in the system.

[0057] Take 20 g of IL in a 250 mL three-necked flask, and remove water at 103°C for 2 h under vacuum, then add 4.88 g of hexamethylene diisocyanate trimer (trade name WANNATE ® , HT-100), first at 30°C for 1.5 h, and then at 80°C for 4 h, and the obtained prepolymer 2 is the ionic liquid dipole unit, which is packaged in a brown glass bottle.

[0058]

[0059] (3) Preparation of azobenzene-based cross-linked polyionic liquid UV photoelectric conversion material (C-AZ-IL)

[0060] Take 10 g of prepolymer 1 and 18.82 g of prepolymer 2 in a 100 mL single-neck flask, and react at 60°C for 0.5 h (not completely reacted, completely reacted and cannot be dissolved after curing, and subsequent devices cannot be prepared by coating), to obtain a cross-linked azobenzene-based polyionic liquid UV photoelectric conversion material (C-AZ-IL), ready for use.

[0061] Comparative Example 1

[0062] This comparative example provides a linear azobenzene-based polyionic liquid UV photoelectric conversion material (L-AL-IL), and the specific preparation steps are as follows:

[0063] (1) Preparation of azobenzene photosensitive unit (prepolymer 1): the same as the preparation steps in Example 1.

[0064] (2) Preparation of dihydroxy ionic liquid prepolymer (prepolymer 3)

[0065] Take 20 g of IL (preparation steps see Example 1) in a 250 mL three-neck flask, and vacuum dehydrate at 103°C for 2 h, then add 2.44 g of hexamethylene diisocyanate (HDI), first react at 30°C for 1.5 h, and then react at 80°C for 4 h, to obtain the prepolymer 3, which is a dihydroxy ionic liquid prepolymer, packaged in a brown glass bottle.

[0066]

[0067] (3) Preparation of azobenzene-based linear polyionic liquid (L-AZ-IL)

[0068] Take 10 g of prepolymer 1 and 17.13 g of prepolymer 3 in a 100 mL single-neck flask, and react at 60°C for 0.5 h (not completely reacted), to obtain an azobenzene-based linear polyionic liquid (L-AZ-IL), ready for use.

[0069] Table 1. Prepolymer formulation table (equivalents)

[0070]

[0071] Table 2. Polymer formulation table (equivalents)

[0072]

[0073] Example 2

[0074] This example provides a photoelectric device with a four-layer structure prepared from the azobenzene-based cross-linked polyionic liquid UV photoelectric conversion material (C-AZ-IL) provided in Example 1, denoted as device 1, and the specific preparation method is as follows:

[0075] a. The PET transparent electrode film with Ni-Cu alloy deposited on the surface was cut into electrode pieces with a size of 1.5 cm x 3 cm for standby use.

[0076] b. The C-AZ-IL mixed solution prepared in Example 1 was coated on the electrode piece using a 20 μm wire bar, with a coating area of 1.5 cm x 1.5 cm, to obtain an electrode piece partially covered with C-AZ-IL. It was placed in an 80 °C oven to continue the cross-linking and curing reaction, and dried to constant weight to obtain a C-AZ-IL partially covered electrode piece, as shown in (a) of Figure 1

[0077] c. Another identical C-AZ-IL partially covered electrode was attached to its surface (C-AZ-IL facing down, C-AZ-IL facing up, and the C-AZ-IL of the two electrode pieces completely overlapping, with the C-AZ-IL-free part facing in two opposite directions). It was pressed at room temperature at a pressure of 10 kN for 5 min to ensure sufficient contact between the C-AZ-IL and the C-AZ-IL, C-AZ-IL and the Ni-Cu alloy electrode, to obtain a double-layer C-AZ-IL electrode piece, as shown in (b) of Figure 1 Figure 1 The core part of the obtained C-AZ-IL UV photovoltaic device with a four-layer structure (device 2) is composed of four layers, from top to bottom: Ni-Cu alloy, C-AZ-IL, C-AZ-IL, and Ni-Cu alloy, with thicknesses of 8 μm, 20 μm, 20 μm, and 8 μm, respectively.

[0078] Comparative Example 2

[0079] This comparative example provides a photovoltaic device with a four-layer structure prepared from the azobenzene-based linear polyionic liquid UV photovoltaic conversion material provided in Comparative Example 1, denoted as device 2, and the preparation method is the same as the main content of Example 2, with the difference being that the C-AZ-IL mixed solution in step b is replaced by the L-AZ-IL mixed solution in Comparative Example 1.

[0080] The obtained L-AZ-IL UV photovoltaic device with a four-layer structure (device 2) has a core part composed of four layers, from top to bottom: Ni-Cu alloy, L-AZ-IL, L-AZ-IL, and Ni-Cu alloy, with thicknesses of 8 μm, 20 μm, 20 μm, and 8 μm, respectively.

[0081] Comparative Example 3

[0082] ​​The comparative example provides preparation of a photovoltaic device with a three-layer structure from the linear azobenzene-based polyionic liquid UV photoelectric conversion material provided by Comparative Example 1, denoted as device 3, and the specific preparation method is as follows:

[0083] a. The PET transparent electrode film with Ni-Cu alloy deposited on the surface was cut into an electrode piece with a size of 1.5 cm x 3 cm for standby use.

[0084] b. The L-AZ-IL mixed solution prepared in Comparative Example 1 was coated on the electrode piece using a 20 μm wire rod, and the coating area was 1.5 cm x 1.5 cm, to obtain an electrode piece partially covered with L-AZ-IL mixed solution. It was placed in an 80°C oven to continue the crosslinking and curing reaction, and dried to constant weight to obtain an electrode piece partially covered with L-AZ-IL.

[0085] c. Another electrode piece without L-AZ-IL coverage was attached to its surface (the conductive surface faced downward and was in full contact with L-AZ-IL). It was pressed at room temperature with a pressure of 10 kN for 5 min to ensure sufficient contact between L-AZ-IL and the Ni-Cu alloy electrode, to obtain a single-layer L-AZ-IL electrode piece. Finally, a copper wire was drawn, and a dimethylsiloxane (PDMS) encapsulation process was used to obtain a conventional L-AZ-IL UV photovoltaic device (device 3) with a three-layer structure, the core part of which is composed of three layers from top to bottom: Ni-Cu alloy, L-AZ-IL, and Ni-Cu alloy, with thicknesses of 8 μm, 20 μm, and 8 μm, respectively.

[0086] (I) Open-circuit voltage test of different devices

[0087] The device 1 prepared in Example 2, the device 2 prepared in Comparative Example 2, and the device 3 prepared in Comparative Example 3 were respectively tested for output open-circuit voltage under UV light irradiation at 6412.8 µm / cm 2 The test results are shown in Table 1. Figure 2

[0088] The results show that the maximum open-circuit voltage value of device 1 is 24.95 V, the maximum open-circuit voltage value of device 2 is 27.36 V, and the maximum open-circuit voltage value of device 3 is 26.97 V. It can be seen that the electrical performance of device 1 is only slightly lower than that of devices 2 and 3, and still has good electrical performance.

[0089] Table 3 Maximum open-circuit voltage values of different devices

[0090]

[0091] (II) Mechanical performance test

[0092] ​Device 1 in Example 2 was subjected to 30 cycles of bending and twisting, and then placed in a 100 °C oven for 2 h to test dimensional stability.

[0093] Figure 3 (a), (b), (c) in FIG. 1 are the initial, after 30 cycles of bending and twisting, and after 2 h in a 100 °C oven, respectively, of the same device 1. As can be seen, device 1 maintained structural integrity and uniformity of appearance after 30 cycles of bending and twisting and high-temperature baking. Figure 4 are the open-circuit voltage test results of the same device 1 initially, after 30 cycles of bending and twisting, and after 2 h in a 100 °C oven. As can be seen, device 1 maintained original output performance after 30 cycles of bending and twisting and high-temperature baking. Thus, the introduction of crosslinked structures increases the resistance of the device to mechanical stress (e.g., bending, pressure), and improves dimensional stability. The four-layer structure also improves the durability of the device. Having two active polymer layers means that if one layer suffers from a minor defect or local stress, the other layer can still function or help distribute the load.

Claims

1. A cross-linked polyionic liquid ultraviolet photoelectric conversion material based on azobenzene, characterized in that, The ultraviolet photoelectric conversion material is polymerized from azobenzene photosensitive units and ionic liquid dipole units; the ionic liquid dipole units have a trimer structure as the crosslinking core and ionic liquid dipole monomer groups grafted to the ends of the structure; the azobenzene photosensitive units are obtained by polymerizing azobenzene monomers and isocyanates; the azobenzene monomer is 4,4'-bis[2-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)ethoxy]azobenzene; The structural formula of the ionic liquid dipole unit is as follows: ； -R represents the ionic liquid dipole monomer group.

2. The azobenzene-based cross-linked polyionic liquid ultraviolet photoelectric conversion material according to claim 1, characterized in that, The isocyanate is one of hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, and isophorone diisocyanate.

3. The cross-linked polyionic liquid ultraviolet photoelectric conversion material based on azobenzene according to claim 1, characterized in that, The ionic liquid dipole monomer group is at least one of imidazole ionic liquid group and quaternary ammonium salt ionic liquid group.

4. The cross-linked polyionic liquid ultraviolet photoelectric conversion material based on azobenzene according to claim 3, characterized in that, The structural formula of the ionic liquid dipole unit is: 。 5. The method for preparing the azobenzene-based cross-linked polyionic liquid ultraviolet photoelectric conversion material according to any one of claims 1-4, characterized in that, Includes the following steps: Preparation of azobenzene photosensitive unit; Preparation of ionic liquid dipole units; Azobenzene photosensitive units and ionic liquid dipole units were reacted at 55-65℃ to obtain a cross-linked polyionic liquid ultraviolet photoelectric conversion material based on azobenzene.

6. The preparation method of the cross-linked polyionic liquid ultraviolet photoelectric conversion material based on azobenzene according to claim 5, characterized in that, The preparation steps of the azobenzene photosensitive unit are as follows: 4,4'-dihydroxyazobenzene, 2-(2-(2-(2-(bromoethoxy)ethoxy)ethoxy)ethanol, carbonate and iodide salt were dissolved in a first organic solvent and reacted at 75-85℃ for 12-14 h. The crude product obtained from the reaction was then extracted, washed and dried to obtain the dark red paste-like target product 4,4'-bis[2-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)ethoxy]azobenzene monomer. The monomers 4,4'-bis[2-(2-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)ethoxy]azobenzene and isocyanate were mixed and reacted at 25-30℃ for 1-1.5 h, and then reacted at 75-85℃ for 2-4 h to obtain the azobenzene photosensitive unit.

7. The preparation method of the cross-linked polyionic liquid ultraviolet photoelectric conversion material based on azobenzene according to claim 6, characterized in that, The molar ratio of 4,4'-dihydroxyazobenzene, 2-(2-(2-(2-(bromoethoxy)ethoxy)ethoxy)ethanol, carbonate, and iodide is 10:(20-21):20:1; the molar ratio of 4,4'-bis[2-(2-(2-(2-hydroxyethoxy)ethoxy)ethoxy)ethoxy]azobenzene monomer to isocyanate is 1:2; the first organic solvent is N,N-dimethylformamide or dimethyl sulfoxide; the carbonate is potassium carbonate or sodium carbonate; the iodide is potassium iodide or sodium iodide; the isocyanate is one of hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, and isophorone diisocyanate.

8. The method for preparing the azobenzene-based cross-linked polyionic liquid ultraviolet photoelectric conversion material according to claim 5, characterized in that, The preparation method of the ionic liquid dipole unit includes: Diethanolamine was added to a second organic solvent and stirred evenly at 55-65°C. Then, bromobutane was added, and the mixture was heated and stirred under reflux at 85-95°C for 45-55 hours. The second organic solvent and unreacted bromobutane were removed by rotary evaporation to obtain a quaternary ammonium salt-Br ionic liquid. The quaternary ammonium salt-Br ionic liquid was mixed with 1-ethyl-3-methylimidazoline bis(trifluoromethanesulfonyl)imine in a third organic solvent and stirred at 25-30°C for 20-30 h, followed by refrigeration at 0-5°C for 18-25 h; then the third organic solvent was removed by rotary evaporation to obtain the quaternary ammonium salt-bis(trifluoromethanesulfonyl)imine ionic liquid monomer. The quaternary ammonium salt-bis(trifluoromethanesulfonyl)imine ionic liquid monomer and the diisocyanate trimer are reacted at 25-30℃ for 1-1.5 h, and then at 75-85℃ for 2-4 h to obtain the ionic liquid dipole unit.

9. The method for preparing the azobenzene-based cross-linked polyionic liquid ultraviolet photoelectric conversion material according to claim 8, characterized in that, The molar ratio of diethanolamine, bromobutane, and 1-ethyl-3-methylimidazoline bis(trifluoromethanesulfonyl)imine is 1:(2-2.2):1; the molar ratio of the quaternary ammonium salt-bis(trifluoromethanesulfonyl)imine ionic liquid monomer to the diisocyanate trimer is 3:1; the diisocyanate trimer is one of hexamethylene diisocyanate trimer, toluene diisocyanate trimer, and isophorone diisocyanate trimer; both the second and third organic solvents are acetonitrile.

10. The application of the azobenzene-based crosslinked polyionic liquid ultraviolet photoelectric conversion material according to any one of claims 1-4 in the fabrication of optoelectronic devices.

11. The application according to claim 10, characterized in that, A photoelectric device is obtained by curing a cross-linked polyionic liquid ultraviolet photoelectric conversion material between two electrode sheets. The specific steps are as follows: Azobenzene photosensitive units and ionic liquid dipole units were reacted at a molar ratio of 3:2 at 55-65℃ for 0.5-1h. The resulting azobenzene-based cross-linked polyionic liquid ultraviolet photoelectric conversion material was then uniformly coated onto two electrode sheets and cured at 75-85℃ to constant weight. The two electrode sheets coated with the azobenzene-based cross-linked polyionic liquid ultraviolet photoelectric conversion material were then bonded together, pressed, and encapsulated to obtain an azobenzene-based cross-linked polyionic liquid ultraviolet optoelectronic device. The thickness of the coated photoelectric conversion material was 15-20μm.

Images