Preparation method and application of polyimide based on bisphenol A diether dianhydride monomer

Abstract

The invention discloses a preparation method and application of a polyimide based on a bisphenol A type diether dianhydride monomer, belonging to the technical field of polymer materials. The invention provides a polyimide with good film-forming performance, high thermal stability and high photoelectric conversion efficiency. The polyimide is obtained by chemical imidization or thermal imidization of polyamic acid obtained by reacting a diamine monomer with a bisphenol A type diether dianhydride monomer. The diamine monomer contains a fluoroboron dipyrrole structure. Both the polyimide skeleton and the fluoroboron dipyrrole structure have excellent thermal and chemical stability. The polymer structure has good film-forming properties and is conducive to forming a stable thin film. The rigid main chain structure of the polyimide reduces molecular vibration. The rigid large π conjugated system of the fluoroboron dipyrrole structure provides not only a wide absorption spectrum but also a high molar absorption coefficient.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and particularly relates to a preparation method and application of a polyimide based on bisphenol A diether dianhydride monomer. Background Art

[0002] Active layer materials for solar cells primarily include metals and their complexes, organic small molecules, and polymers. Common methods for preparing the active layer of organic solar cells include thermal evaporation, solution spin coating, and inkjet printing. Organic solar cells are typically fabricated using vacuum evaporation, the mainstream fabrication process. However, the evaporation process is complex and time-consuming. On the one hand, the excellent self-crystallization properties of organic small molecules can easily damage the film's flatness and transport properties over time; on the other hand, obtaining uniform thin films using solution processing is difficult. Therefore, solution processing, with its advantages of efficiency, simplicity, and low cost, has become a research hotspot. Active layers for polymer solar cells are typically fabricated using solution spin coating and inkjet printing. This is primarily due to the excellent film-forming properties, structural stability, and thermodynamic stability of polymers, making them suitable for the fabrication of large-area, transparent, and flexible devices. Therefore, preparing an active layer with excellent film structural stability is particularly important. Polymer materials not only allow for device performance to be manipulated through chemical structure design but also offer excellent machinability, chemical resistance, and radiation resistance, making them the optimal choice for active layer materials in most organic solar cells. Polyimide (PI) contains a repeated imide aromatic ring conjugated system in its structure, which has the advantages of a strong structure, a high thermal decomposition temperature, and good film-forming properties. This has enabled it to make great progress in the fields of organic electronic devices such as organic electrical storage, nonlinear optical materials, liquid crystal display alignment film materials, liquid crystal display phase difference compensation film materials, organic solar cells, and electroluminescent diodes.

[0003] These excellent overall properties stem from the conjugation between the main chain and side chains of the PI molecule and the stacking of the molecular chain structure. A higher degree of conjugation results in denser molecular chain stacking, higher thermal stability, and better corrosion resistance. However, the strong interchain interactions can make PI less soluble and difficult to melt, resulting in poor flexibility and brittle cracking of the prepared PI films. Introducing functional and fluorescent groups into PI can maintain PI's excellent thermal stability, photophysical, and electrochemical properties while improving its organic solubility and processability. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings of the prior art, the present invention designed and synthesized a diamine monomer with a fluoroborane dipyrrole structure, based on the copolymerization of bisphenol A diether dianhydride monomer and diamine monomer, to provide a polyimide with good film-forming performance, high thermal stability and high photoelectric conversion efficiency.

[0005] The technical solutions for achieving the purpose of the present invention are as follows:

[0006] A method for preparing a polyimide based on bisphenol A diether dianhydride monomer comprises the following steps:

[0007] In an inert gas atmosphere, a diamine monomer and a bisphenol A diether dianhydride monomer are dissolved in a polar aprotic solvent in a reaction kettle, and the mixture is stirred and reacted for 12 to 48 hours to obtain polyamic acid, which is then chemically imidized or thermally imidized to obtain polyimide;

[0008] The diamine monomer is one or more of the following molecular structures:

[0009]

[0010]

[0011] Preferably, the polar aprotic solvent is one or more of dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, dimethylacetamide, N-methylpyrrolidone and 1,4-dioxane.

[0012] Preferably, the temperature of the stirring reaction is 0-40°C; the catalyst used in the chemical imidization method is one or more of acetic anhydride and triethylamine, acetic anhydride and pyridine, and acetic anhydride and imidazole; the reaction temperature of the chemical imidization method is 60-100°C; the reaction temperature of the thermal imidization method is greater than 150°C.

[0013] Preferably, the diamine monomer preparation method is as follows:

[0014] S1. 3,5-Dinitrobenzoyl chloride and p-aminobenzaldehyde are amidated to give 3,5-Dinitro-N-phenylbenzamide;

[0015] S2. The 3,5-dinitro-N-phenylbenzamide obtained in step S1 is condensed with 2,4-dimethylpyrrole to obtain compound I, which is then condensed with 2-phenyl-4-methyl-1H-pyrrole to obtain compound II, which is then condensed with 2-(4-methoxyphenyl)-4-methylpyrrole to obtain compound III, which is then condensed with 2-(4-tert-butylphenyl)-4-methylpyrrole to obtain compound IV;

[0016] S3. Compound I, compound II, compound III, and compound IV obtained in step S2 are respectively reduced and then treated with a base and boron trifluoride etherate complex to obtain molecular structures of formula I, formula II, formula III, and formula IV, respectively;

[0017] S4. Nucleophilic addition of 4-diphenylaminobenzaldehyde to the molecular structure of formula I obtained in step S3 is followed by dehydration to obtain the molecular structure of formula V.

[0018] Preferably, the specific operation of step S1 is: at a temperature of 0 to 5°C, 2eq of 3,5-dinitrobenzoyl chloride and 2 to 3eq of triethylamine are added to a reactor, dimethylformamide is added to dissolve it, and stirred, 1 to 1.5eq of p-aminobenzaldehyde is added dropwise to the reaction flask, and the dripping is completed over 10 to 20 minutes, the temperature is increased to 40 to 50°C, the reaction is carried out for 4 to 6 hours, and the reaction is cooled to room temperature. A mixture of methanol and water is poured into the reaction solution, and the volume ratio of methanol to water is 2:1. Solid precipitates, and the filter cake is filtered, washed twice with sodium hydroxide solution, and recrystallized with methanol to obtain 3,5-dinitro-N-phenylbenzamide.

[0019] Preferably, the specific operation of step S2 is as follows: under a nitrogen atmosphere, 1eq of 3,5-dinitro-N-phenylbenzamide and 2-2.5eq of 2,4-dimethylpyrrole are dissolved in chloroform, 0.5-1wt% of trifluoroacetic acid of the total system is added dropwise, and stirred at room temperature for 12-14h, 1-1.2eq of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is dissolved in chloroform and added to the mixture, and the mixture is heated to 45-50°C and continued. The mixture was stirred for 20 to 30 minutes, and the resulting solution was washed with water at least twice. The organic phase was concentrated and purified by column chromatography to obtain compound I. 2,4-dimethylpyrrole was replaced by 2-phenyl-4-methyl-1H-pyrrole to obtain compound II; 2,4-dimethylpyrrole was replaced by 2-(4-methoxyphenyl)-4-methylpyrrole to obtain compound III; 2,4-dimethylpyrrole was replaced by 2-(4-tert-butylphenyl)-4-methylpyrrole to obtain compound IV.

[0020] Preferably, the specific operation of step S3 is: under a nitrogen atmosphere, 1eq of compound I is added to a reactor, and then a mixed solution of ethanol and water is added, the temperature is raised to 45-55 ° C, 6-8eq of iron powder and 20-30eq of acetic acid are added, the temperature is raised to 60-70 ° C, and stirred for 2-3h, cooled to room temperature, filtered, and the obtained liquid is evaporated to remove most of the ethanol, extracted with chloroform, and the obtained chloroform is washed with ammonia water once, the filtrate is dried over anhydrous magnesium sulfate, filtered, and the obtained filtrate is evaporated, and the obtained solid is dissolved in chloroform, and 1.5eq of triethylamine is added. Stir for 20 to 30 minutes, then add 2.0 eq of boron trifluoride ether complex, stir at 45 to 50° C. for 2 to 3 hours, add dichloromethane to dilute the mixture, wash three times with saturated sodium carbonate solution, collect the organic phase, dry it over anhydrous magnesium sulfate, and filter it. Remove excess tetrahydrofuran and ethyl acetate by rotary evaporation, and purify it by column chromatography to obtain a molecular structure of formula I; replace compound I with compound II, compound III, and compound IV in sequence, and repeat the specific reaction operation of S3 to obtain molecular structures of formula II, formula III, and formula IV.

[0021] Preferably, the specific operation of step S4 is: under a nitrogen atmosphere, 1 eq of the molecular structure of formula I obtained in step S3 is added to a reaction kettle and dissolved with anhydrous acetonitrile, then 3 to 4 eq of 4-diphenylaminobenzaldehyde is added, followed by 5 to 6 eq of acetic acid and 5 to 6 eq of pyridine, heated to 85 to 95 ° C, stirred for 2 to 3 hours, the solvent was evaporated, and purified by column chromatography to obtain a molecular structure of formula V.

[0022] Preferably, the diamine monomer has a molecular structure of formula V.

[0023] The present invention also protects a polyimide based on bisphenol A diether dianhydride monomer, which is prepared by the above-mentioned preparation method of the polyimide based on bisphenol A diether dianhydride monomer.

[0024] The present invention also protects the application of a polyimide based on bisphenol A diether dianhydride monomer in an active layer of an organic solar cell.

[0025] Beneficial effects

[0026] The present invention has the following beneficial effects:

[0027] 1. The stability of the active layer of organic solar cells is crucial to improving the life of solar cells. They need to remain stable under light, heat and environmental factors. The polyimide skeleton and fluoroboron dipyrrole structure both have excellent thermal and chemical stability, and the polymer structure has good film-forming properties, which helps to form a stable film.

[0028] 2. The imide group has strong electron-withdrawing properties, which is beneficial to lowering the LUMO energy level. It can form a suitable energy level difference with common donor materials and promote exciton separation.

[0029] 3. The rigid main chain structure reduces the vibration of the molecule and reduces the energy loss in the form of heat through vibration. The rigid large π conjugated system not only provides a wider absorption spectrum but also a higher molar absorption coefficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the synthesis route of the diamine monomer of Preparation Example 4 of the present invention;

[0031] Figure 2 This is a schematic structural diagram of the polyimide prepared in Example 5 of the present invention;

[0032] Figure 3 This is the H NMR spectrum of the diamine monomer prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0034] In the examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0035] The raw materials and equipment used in the embodiments and comparative examples are described below:

[0036] Bisphenol A diether dianhydride monomer: Liaoning Xingfu New Materials;

[0037] 3,5-Dinitrobenzoyl chloride: Product No. D100649, Shanghai Aladdin Reagent;

[0038] p-Aminobenzaldehyde: Product No. A303975, Shanghai Aladdin Reagent;

[0039] 2,4-Dimethylpyrrole: Product No. D123132, Shanghai Aladdin Reagent;

[0040] Acetic anhydride: Sinopharm Reagent;

[0041] Triethylamine: Product No. T103285, Shanghai Aladdin Reagent;

[0042] Boron trifluoride etherate complex: Product No. B104430, Shanghai Aladdin Reagent;

[0043] 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone: Product No. D109444, Shanghai Aladdin Reagent;

[0044] Acetic acid: Product No. A406437, Shanghai Aladdin Reagent;

[0045] 4-Diphenylaminobenzaldehyde: D109427, Shanghai Aladdin Reagent;

[0046] Pyridine: Sinopharm Reagent.

[0047] The following are the test methods for the performance parameters involved in the present invention:

[0048] NMR spectra: 1H NMR spectra of the compounds were obtained using a 400 MHz Bruker NMR instrument. Deuterated dimethyl sulfoxide (DDMSO) was used as the solvent, and 1% tetramethylsilane was added. Raw data were obtained by 16 scans and analyzed using software.

[0049] Fluorescence emission spectroscopy: Fluorescence spectrophotometer, Shanghai Lingguang Technology Co., Ltd.;

[0050] Ultraviolet absorption spectrum: UV-visible spectrophotometer, Shanghai Meixi UV-1800;

[0051] Photoelectric conversion efficiency: Keithley 2400 source meter (AM1.5 G, 100mW / cm 2 )test.

[0052] Preparation Example 1

[0053] At 0°C, add 2eq of 3,5-dinitrobenzoyl chloride and 2.5eq of triethylamine to the reactor, add dimethylformamide to dissolve it, stir, add 1.5eq of p-aminobenzaldehyde dropwise to the reaction flask, complete the dropwise addition over 20 minutes, raise the temperature to 40°C, react for 4 hours, cool to room temperature, pour a mixture of methanol and water into the reaction solution, the volume ratio of methanol to water is 2:1, solid precipitates, filter, wash the filter cake twice with sodium hydroxide solution, and recrystallize with methanol to obtain 3,5-dinitro-N-phenylbenzamide.

[0054] Preparation Example 2

[0055] Under a nitrogen atmosphere, 1 eq of 3,5-dinitro-N-phenylbenzamide and 2 eq of 2,4-dimethylpyrrole were dissolved in chloroform, and 1 wt% of trifluoroacetic acid was added dropwise. The mixture was stirred at room temperature for 12 h. 1.2 eq of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone was dissolved in chloroform and added to the mixture. The mixture was heated to 45 ° C and stirred for 30 min. The resulting solution was washed three times with water, and the organic phase was concentrated and purified by column chromatography to obtain compound I.

[0056] Preparation Example 3

[0057] Under a nitrogen atmosphere, 1 eq of compound I was added to a reaction kettle, and a mixed solution of ethanol and water was added to each portion. The temperature was raised to 45-55 ° C, 6-8 eq of iron powder and 20-30 eq of acetic acid were added, the temperature was raised to 60-70 ° C and stirred for 2-3 hours, cooled to room temperature, and filtered. The resulting liquid was evaporated to remove most of the ethanol, extracted with chloroform, and the resulting chloroform was washed once with ammonia water. The filtrate was dried over anhydrous magnesium sulfate and filtered. After the filtrate was evaporated, the resulting solid was dissolved in chloroform, 1.5 eq of triethylamine was added and stirred for 20-30 minutes, and then 2.0 eq of boron trifluoride ether complex was added and stirred at 50 ° C for 2 hours. Dichloromethane was added to dilute the mixture and washed three times with saturated sodium carbonate solution. The organic phase was collected, dried over anhydrous magnesium sulfate, and filtered. The excess tetrahydrofuran and ethyl acetate were removed by rotary evaporation and purified by column chromatography to obtain the molecular structure of formula I.

[0058] Preparation Example 4

[0059] Under a nitrogen atmosphere, 1 eq of the molecular structure of Formula I obtained in Preparation Example 3 was added to a reaction kettle and dissolved in anhydrous acetonitrile. Then, 4 eq of 4-diphenylaminobenzaldehyde was added, followed by 6 eq of acetic acid and 6 eq of pyridine. The mixture was heated to 95° C. and stirred for 3 h. The solvent was evaporated and purified by column chromatography to obtain a molecular structure of Formula V.

[0060] Preparation Example 5

[0061] Under a nitrogen atmosphere, 1 eq of the molecular structure of formula V obtained in the preparation example and 1.1 eq of bisphenol A diether dianhydride monomer were dispersed in DMF solvent, reacted at room temperature for 16 h, and then 3 eq of a mixed solution of acetic anhydride and pyridine in a volume ratio of 1:1 was added. The mixture was reacted at 90°C for 8 h, cooled to room temperature, and the solution was poured into alcohol. The solid was filtered to obtain a solid, washed twice with methanol, and dried to obtain a polyimide.

[0062] Example 1

[0063] Organic solar cell device: indium tin oxide (ITO) is selected as the transparent electrode, polyethoxythiophene (PEDOT): polystyrene sulfonic acid (PSS) is selected as the hole transport layer, benzo[1,2-b:4,5-b']dithiophene (BDT) and dithienylbenzo[1',2'-c:4',5'-c']dithiophene-4,8-dione (BDD) copolymer is selected as the active layer donor material, the polyimide obtained in Preparation Example 5 is selected as the active layer acceptor material, a polyfluorene derivative (PFN) is selected as the electron transport layer, and aluminum is selected as the cathode electrode; wherein the mass ratio of the active layer donor material to the active layer acceptor material is 1:1.4.

[0064] Comparative Example 1

[0065] The difference from Example 1 is that the active layer receptor material is the molecular structure of Formula V obtained in Preparation Example 4.

[0066] Table 1 Performance tests of monomers, polymers and their devices

[0067]

[0068] It can be seen from the photoelectric conversion efficiency data of the embodiments and comparative examples in Table 1 that the photoelectric conversion efficiency is higher after polymerization. After polymerization, the electron-donating amino structure of the monomer molecular structure is converted into the electron-withdrawing structure of the imide, which lowers the LUMO energy level, forms a suitable energy level difference with the donor material, and promotes the separation of excitons.

[0069] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a polyimide based on bisphenol A diether dianhydride monomer, characterized in that: The following steps are involved: In an inert gas atmosphere, a diamine monomer and a bisphenol A diether dianhydride monomer are dissolved in a polar aprotic solvent in a reaction kettle, and the mixture is stirred continuously to react to obtain polyamic acid, which is then chemically imidized or thermally imidized to obtain polyimide; The diamine monomer is one or more of the following molecular structures:

2. The method for preparing a polyimide based on bisphenol A diether dianhydride monomer according to claim 1, wherein: The polar aprotic solvent is one or more of dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, dimethylacetamide, N-methylpyrrolidone and 1,4-dioxane.

3. The method for preparing a polyimide based on bisphenol A diether dianhydride monomer according to claim 1, wherein: The temperature of the stirring reaction is 0 to 40° C.; the catalyst used in the chemical imidization method is one or more of acetic anhydride and triethylamine, acetic anhydride and pyridine, and acetic anhydride and imidazole; the reaction temperature of the chemical imidization method is 60 to 100° C.; the reaction temperature of the thermal imidization method is greater than 150° C.

4. The method for preparing a polyimide based on bisphenol A diether dianhydride monomer according to claim 1, wherein: The diamine monomer preparation method is as follows: S1. 3,5-Dinitrobenzoyl chloride and p-aminobenzaldehyde are amidated to give 3,5-Dinitro-N-phenylbenzamide; S2. The 3,5-dinitro-N-phenylbenzamide obtained in step S1 is condensed with 2,4-dimethylpyrrole to obtain compound I, which is then condensed with 2-phenyl-4-methyl-1H-pyrrole to obtain compound II, which is then condensed with 2-(4-methoxyphenyl)-4-methylpyrrole to obtain compound III, which is then condensed with 2-(4-tert-butylphenyl)-4-methylpyrrole to obtain compound IV; S3. Compound I, compound II, compound III, and compound IV obtained in step S2 are respectively reduced and then treated with a base and boron trifluoride etherate complex to obtain molecular structures of formula I, formula II, formula III, and formula IV, respectively; S4. Nucleophilic addition of 4-diphenylaminobenzaldehyde to the molecular structure of formula I obtained in step S3 is followed by dehydration to obtain the molecular structure of formula V.

5. The method for preparing a polyimide based on bisphenol A diether dianhydride monomer according to claim 4, wherein: The specific operation of step S1 is as follows: at a temperature of 0 to 5° C., 2 eq of 3,5-dinitrobenzoyl chloride and 2 to 3 eq of triethylamine are added to a reaction kettle, dimethylformamide is added to dissolve it, and the mixture is stirred. 1 to 1.5 eq of p-aminobenzaldehyde is added dropwise to the reaction flask over a period of 10 to 20 minutes. The temperature is raised to 40 to 50° C., the mixture is reacted for 4 to 6 hours, and the mixture is cooled to room temperature. A mixture of methanol and water is poured into the reaction solution in a volume ratio of 2:

1. Solid precipitates, and the solid is filtered. The filter cake is washed at least twice with sodium hydroxide solution and recrystallized with methanol to obtain 3,5-dinitro-N-phenylbenzamide.

6. The method for preparing a polyimide based on bisphenol A diether dianhydride monomer according to claim 4, wherein: The specific operation of step S2 is as follows: under a nitrogen atmosphere, 1eq of 3,5-dinitro-N-phenylbenzamide and 2-2.5eq of 2,4-dimethylpyrrole are dissolved in chloroform, 0.5-1wt% of trifluoroacetic acid is added dropwise, and the mixture is stirred at room temperature for 12-14h. 1-1.2eq of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is dissolved in chloroform and added to the mixture, and the mixture is heated to 45-50°C and stirred continuously. The mixture was stirred for 20 to 30 minutes, and the resulting solution was washed with water at least twice. The organic phase was concentrated and purified by column chromatography to obtain compound I; 2,4-dimethylpyrrole was replaced by 2-phenyl-4-methyl-1H-pyrrole to obtain compound II; 2,4-dimethylpyrrole was replaced by 2-(4-methoxyphenyl)-4-methylpyrrole to obtain compound III; 2,4-dimethylpyrrole was replaced by 2-(4-tert-butylphenyl)-4-methylpyrrole to obtain compound IV.

7. The method for preparing a polyimide based on bisphenol A diether dianhydride monomer according to claim 4, wherein: The specific operation of step S3 is as follows: under a nitrogen atmosphere, 1eq of compound I is added to a reactor, and then a mixed solution of ethanol and water is added, the temperature is raised to 45-55 ° C, 6-8eq of iron powder and 20-30eq of acetic acid are added, the temperature is raised to 60-70 ° C and stirred for 2-3h, cooled to room temperature, filtered, and the resulting liquid is evaporated to remove most of the ethanol, extracted with chloroform, and the resulting chloroform is washed with ammonia water 1-2 times. The filtrate is dried over anhydrous magnesium sulfate and filtered. After the filtrate is evaporated, the resulting solid is dissolved in chloroform and 1.5eq of triethylamine is added and stirred. The mixture was stirred for 20 to 30 minutes, and then 2.0 eq of boron trifluoride ether complex was added, stirred at 45 to 50 ° C for 2 to 3 hours, and dichloromethane was added to dilute the mixture. The mixture was washed with saturated sodium carbonate solution at least twice, and the organic phase was collected, dried over anhydrous magnesium sulfate, and then filtered. The excess tetrahydrofuran and ethyl acetate were removed by rotary evaporation, and purified by column chromatography to obtain a molecular structure of formula I; compound I was replaced with compound II, compound III and compound IV in sequence, and the specific reaction operation of S3 was repeated to obtain molecular structures of formula II, formula III and formula IV.

8. The method for preparing a polyimide based on bisphenol A diether dianhydride monomer according to claim 4, wherein: The specific operation of step S4 is as follows: under a nitrogen atmosphere, 1 eq of the molecular structure of formula I obtained in step S3 is added to a reaction kettle and dissolved in anhydrous acetonitrile, then 3 to 4 eq of 4-diphenylaminobenzaldehyde is added, followed by 5 to 6 eq of acetic acid and 5 to 6 eq of pyridine, heated to 85 to 95° C., stirred for 2 to 3 h, the solvent was evaporated, and purified by column chromatography to obtain a molecular structure of formula V.

9. A polyimide based on bisphenol A diether dianhydride monomer, characterized in that: The polyimide is prepared by the preparation method of a bisphenol A diether dianhydride monomer according to any one of claims 1 to 8.

10. Use of the polyimide based on bisphenol A diether dianhydride monomer as claimed in claim 9 in an active layer of an organic solar cell.

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