Conjugated polymer film as well as preparation method and application thereof

Abstract

The invention relates to the technical field of photoelectricity, and discloses a conjugated polymer film as well as a preparation method and application thereof. In the presence of a first solvent and a first catalyst, (4, 8-bis (5-(2-ethylhexyl)-4-fluorothienyl) benzo [1, 2-b: 4, 5-b '] dithienyl) bis (trimethyltin), 1, 3-bis (5-bromothiophene-2-yl)-5, 7-bis (2-ethylhexyl) benzo [1, 2-C: 4, 5-C'] dithiophene-4, 8-diketone and a monomer as shown in a formula I are subjected to a ternary polymerization reaction to obtain a ternary conjugated polymer; and blending the obtained ternary conjugated polymer, a second solvent, a cross-linking agent and a second catalyst to form a film, and annealing to obtain the conjugated polymer film. The conjugated polymer film can be used as a light absorption layer for preparing an organic electronic device. According to the conjugated polymer film obtained by the method disclosed by the invention, the mechanical property is obviously improved on the basis of ensuring the photoelectric property; according to the invention, an in-situ cross-linking strategy is adopted, so that the solution processing performance is ensured, the operation is simple, and the controllability of a polymer structure and the batch repeatability are high; # imgabs0 #

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic technologies, and particularly to a conjugated polymer thin film, a preparation method thereof, and an application thereof. Background Art

[0002] Conjugated polymers are a class of polymer materials with a π-π conjugated main chain structure. Due to their excellent optoelectronic properties (such as high carrier mobility, adjustable optical bandgap) and good solution processability, they show great application potential in the fields of flexible electronics, organic solar cells, organic field-effect transistors, sensors, and bioelectronics. However, compared with traditional flexible polymer materials, conjugated polymers usually exhibit poor mechanical properties, such as high brittleness, low ductility, insufficient tensile strength, etc. These defects in mechanical properties severely limit their practical applications in flexible devices, especially in scenarios where repeated deformation or mechanical stress needs to be endured. Therefore, improving the mechanical properties of conjugated polymers has become an important research direction in the field of materials science in recent years.

[0003] The mechanical properties of conjugated polymers are closely related to factors such as their molecular structure, intermolecular interactions, crystallinity, and film morphology. Traditional conjugated polymers usually have a rigid main chain structure, and there are strong π-π interactions between molecular chains. Although this is beneficial to charge transport, it also increases the brittleness of the material. To improve their mechanical properties, researchers have conducted in-depth studies from multiple aspects such as molecular design, microstructure regulation, and composite material preparation. For example, physically blending conjugated polymers with elastomers or other polymer materials to improve their mechanical properties. However, physical blending may lead to phase separation, which in turn affects the uniformity of the material and the performance of electronic devices. Flexible spacer groups or side chains can also be introduced into the conjugated main chain to effectively reduce the rigidity of the material and improve its ductility. However, introducing flexible side chains may reduce the charge transport ability, and too long side chains will also cause disordered molecular packing, affecting crystallinity and optoelectronic properties, etc.

[0004] In addition, a crosslinking strategy can be adopted, either by first polymerizing and then crosslinking (introducing crosslinkable groups into the conjugated semiconductor side chain), or directly polymerizing and crosslinking (directly introducing a crosslinked structure during the preparation of the conjugated polymer), to construct a light-absorbing layer containing a crosslinked structure, inhibit the movement and slip of molecular chains, and enhance intermolecular interactions, thereby improving the mechanical properties of the light-absorbing layer. However, the existing crosslinking strategies have problems such as complex preparation processes, difficult precise control of polymer structures, poor batch repeatability, the risk of photo-crosslinking-induced decomposition, the need to strictly control the molecular weight to ensure solution processability, and potential negative impacts on optoelectronic properties.

[0005] Therefore, there is a need to develop a new conjugate polymer cross-linking strategy to simplify the preparation process, improve the structural controllability and batch repeatability, and ensure solution processability, aiming to significantly enhance the mechanical properties without sacrificing the optoelectronic properties as much as possible. Summary of the Invention

[0006] The object of the present invention is to overcome the problems existing in the prior art and provide a conjugate polymer thin film, a preparation method thereof and an application.

[0007] To achieve the above object, in the first aspect of the present invention, a preparation method of a conjugate polymer thin film is provided, wherein the method comprises the following steps:

[0008] (1) In the presence of a first solvent and a first catalyst, (4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene)bis(trimethylstannyl), 1,3-bis(5-bromothiophen-2-yl)-5,7-bis(2-ethylhexyl)benzo[1,2-c:4,5-c']dithiophene-4,8-dione and a monomer shown in Formula I are subjected to a ternary copolymerization reaction to obtain a ternary conjugate polymer;

[0009] (2) The ternary conjugate polymer obtained in step (1), a second solvent, a cross-linking agent and a second catalyst are blended and formed into a film, and annealed to obtain the conjugate polymer thin film;

[0010]

[0011]

[0012] In the second aspect of the present invention, a conjugate polymer thin film obtained by the preparation method according to the first aspect is provided.

[0013] In the third aspect of the present invention, an application of the conjugate polymer thin film according to the second aspect in the preparation of an organic electronic device is provided.

[0014] In the fourth aspect of the present invention, an organic solar cell comprising the conjugate polymer thin film according to the second aspect as a light absorption layer is provided.

[0015] By the above technical solutions, the beneficial technical effects obtained by the present invention are as follows:

[0016] (1) The conjugate polymer thin film obtained by the method of the present invention has significantly improved mechanical properties on the basis of ensuring optoelectronic properties;

[0017] (2) The present invention adopts an in-situ cross-linking strategy to ensure solution processability, is simple to operate, and has high polymer structure controllability and batch repeatability. Brief Description of the Drawings

[0018] Figure 1 It is the synthesis route of the monomer of Formula I in the preparation example of the present invention.

[0019] Figure 2 It is the 1H NMR spectrum of the monomer of Formula I in the preparation example of the present invention.

[0020] Figure 3 It is the preparation method of PM6-OH in Examples 1-3 of the present invention.

[0021] Figure 4 It is the chemical structural formula of the crosslinking agent hexamethylene diisocyanate used in Examples 4, 6, and 8 of the present invention.

[0022] Figure 5 It is the chemical structural formula of the crosslinking agent hexamethylene diisocyanate trimer used in Examples 5, 7, and 9 of the present invention.

[0023] Figure 6 It is the preparation method of PM6 in Comparative Example 1.

[0024] Figure 7 It is the stress-strain curve of the conjugated polymer film in Examples 4, 5 and Comparative Example 1.

[0025] Figure 8 It is the stress-strain curve of the conjugated polymer film in Examples 6, 7 and Comparative Example 1.

[0026] Figure 9 It is the stress-strain curve of the conjugated polymer film in Examples 8, 9 and Comparative Example 1.

[0027] Figure 10 It is the current density-voltage curve of the organic solar cells prepared in Example 10 and Comparative Example 2. Detailed Description of the Invention

[0028] The endpoints and any values disclosed herein are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0029] The first aspect of the present invention provides a method for preparing a conjugated polymer film, wherein the method comprises the following steps:

[0030] (1) In the presence of a first solvent and a first catalyst, (4,8-bis(5-(2-ethylhexyl)-4-fluorothienyl)benzo[1,2-b:4,5-b']dithienyl)bis(trimethyltin) (BDT), 1,3-bis(5-bromothiophen-2-yl)-5,7-bis(2-ethylhexyl)benzo[1,2-c:4,5-c']dithiophene-4,8-dione (BDD) and a monomer represented by formula I are subjected to a ternary copolymerization reaction to obtain a ternary conjugated polymer;

[0031] (2) The ternary conjugated polymer obtained in step (1), a second solvent, a crosslinking agent and a second catalyst are blended and formed into a film, and annealed to obtain the conjugated polymer film;

[0032]

[0033] In the preparation of the conjugated polymer of the present invention, a monomer represented by formula I (which can be named 2,5-dibromothiophene-3-carboxylate dodecanol) is added, so that in-situ crosslinking (crosslinking occurs after spin coating) can be carried out to ensure solution processability; the prepared conjugated polymer film not only improves the mechanical properties (such as tensile properties), but also can maintain or even improve the optoelectronic properties when used in electronic devices.

[0034] In some embodiments of the present invention, the first solvent is toluene.

[0035] In some embodiments of the present invention, the first catalyst is tetrakis(triphenylphosphine)palladium.

[0036] In some embodiments of the present invention, the dosage of the first catalyst is 1-5 mol%, preferably 2 mol%, based on the mass of (4,8-bis(5-(2-ethylhexyl)-4-fluorothienyl)benzo[1,2-b:4,5-b']dithienyl)bis(trimethyltin).

[0037] In some embodiments of the present invention, in step (1), the molar ratio of (4,8-bis(5-(2-ethylhexyl)-4-fluorothienyl)benzo[1,2-b:4,5-b']dithienyl)bis(trimethyltin), 1,3-bis(5-bromothiophen-2-yl)-5,7-bis(2-ethylhexyl)benzo[1,2-c:4,5-c']dithiophene-4,8-dione and the monomer represented by formula I is 1:0.8-0.95:0.05-0.2, preferably 1:0.9:0.1. In the present invention, controlling the molar content of the monomer represented by formula I within a specific range can ensure both the mechanical properties and optoelectronic properties of the film.

[0038] In some embodiments of the present invention, the second solvent is selected from at least one of chlorobenzene, toluene and chloroform.

[0039] In some embodiments of the present invention, the second catalyst is selected from at least one of dibutyltin dilaurate, stannous octoate, bismuth isooctoate, and triethylenediamine.

[0040] In some embodiments of the present invention, the amount of the second catalyst is 1-5% of the mass of the terpolymer conjugate obtained in step (1), preferably 2%.

[0041] In some embodiments of the present invention, the crosslinking agent contains a functional group capable of undergoing a crosslinking reaction with a hydroxyl group, preferably selected from at least one of a methacrylate group, a carboxyl group, an epoxy group, and an isocyanate group, and preferably an isocyanate group.

[0042] In some embodiments of the present invention, the number of functional groups in the crosslinking agent is at least 2.

[0043] In some embodiments of the present invention, the molar ratio of the functional group in the crosslinking agent to the hydroxyl group in the monomer represented by formula I is 1:1.

[0044] In some embodiments of the present invention, the crosslinking agent is selected from at least one of hexamethylene diisocyanate, hexamethylene diisocyanate trimer, L-lysine triisocyanate, and diphenylmethane diisocyanate.

[0045] In some embodiments of the present invention, the synthesis method of the monomer represented by formula I includes: reacting 2,5-dibromothiophene-3-carboxylic acid and dodecane diol in a protective atmosphere to obtain the monomer represented by formula I.

[0046] In some embodiments of the present invention, the solvent for the reaction is a mixed solvent of dichloromethane and dimethyl sulfoxide.

[0047] In some embodiments of the present invention, the catalyst for the reaction is 4-dimethylaminopyridine (DMAP) and N,N'-dicyclohexylcarbodiimide (DCC).

[0048] In some embodiments of the present invention, the gas of the protective atmosphere is nitrogen.

[0049] In some embodiments of the present invention, the conditions for the reaction include: room temperature; the time is 32 h.

[0050] In some embodiments of the present invention, the product of the reaction is subjected to extraction, drying, column chromatography, and recrystallization to obtain the monomer represented by formula I.

[0051] In some embodiments of the present invention, the conditions for the terpolymerization reaction in step (1) include: a protective atmosphere; the temperature is 110-130 °C, preferably 115 °C; the time is 48-96 h, preferably 72 h.

[0052] In some embodiments of the present invention, the gas of the protective atmosphere is nitrogen.

[0053] In some embodiments of the present invention, the conditions of the annealing in step (2) include: the temperature is 80 - 100 °C, preferably 80 °C; the time is 10 - 30 min, preferably 20 min.

[0054] The second aspect of the present invention provides a conjugated polymer film obtained by the preparation method according to the first aspect.

[0055] The third aspect of the present invention provides the application of the conjugated polymer film described in the second aspect in the preparation of organic electronic devices.

[0056] In some embodiments of the present invention, the conjugated polymer film serves as a light absorption layer.

[0057] In some embodiments of the present invention, the organic electronic device is an organic solar cell.

[0058] The fourth aspect of the present invention provides an organic solar cell including the conjugated polymer film described in the second aspect as a light absorption layer.

[0059] The light absorption layer further includes a small molecule acceptor.

[0060] The present invention will be described in detail below through examples.

[0061] In the following examples and comparative examples, those without specific conditions indicated are carried out according to conventional conditions or conditions recommended by the manufacturer. For the reagents or instruments without the manufacturer indicated, they are all conventional products that can be obtained through commercial purchase.

[0062] Preparation Example

[0063] This preparation example provides a synthesis method of a monomer shown in Formula I containing -OH side chains. The reaction process is as Figure 1 shown, and the specific steps are as follows:

[0064] (1) Using a mixed solvent of dichloromethane and DMSO as the reaction solvent, dissolve the monomer 2,5 - dibromo - thiophene - 3 - carboxylic acid, dodecane diol, 4 - dimethylaminopyridine (DMAP), and N,N - dicyclohexylcarbodiimide (DCC), and react at room temperature for 32 h under the protection of a nitrogen atmosphere;

[0065] (2) After the reaction is completed, add water and dichloromethane for extraction, and then dehydrate and dry with anhydrous sodium sulfate;

[0066] (3) Use petroleum ether and ethyl acetate (volume ratio 2:1) as the eluent for column chromatography;

[0067] (4) Recrystallize the obtained liquid three times with petroleum ether to obtain the target product: the monomer shown in Formula I.

[0068] The 1H NMR spectrum of the monomer shown in Formula I is as Figure 2 shown. 1 H NMR (400 MHz, CDCl3) δ: 7.34 (s, 1H), 4.29 - 4.24 (t, 2H), 3.68 - 3.59 (q, 2H), 1.79 - 1.68 (m, 3H), 1.62 - 1.51 (m, 7H), 1.48 - 1.16 (m, 20H).

[0069] Example 1

[0070] As Figure 3 shown, this example provides a method for preparing a conjugated polymer with a side chain containing 5 mol% -OH groups. The specific steps are as follows:

[0071] (1) Take 423 mg of BDT, 327 mg of BDD and 10.6 mg of the monomer prepared in the preparation example (the molar ratio of the three monomers is 1:0.95:0.05) in a polymerization tube, add 6 mL of toluene, and stir for 10 min until the monomers are completely dissolved;

[0072] (2) Add 10.39 mg of tetrakis(triphenylphosphine)palladium catalyst;

[0073] (3) Evacuate and refill with nitrogen 10 times, transfer the polymerization tube to an oil bath at 115 °C and react for 72 h;

[0074] (4) After the reaction is completed, precipitate the product in methanol;

[0075] (5) Soxhlet extract the product with methanol, petroleum ether, and dichloromethane in sequence;

[0076] (6) Heat and dissolve the Soxhlet-extracted product in chlorobenzene for 1 h;

[0077] (7) After filtering the solution, precipitate it again in methanol;

[0078] (8) After suction filtration, dry the precipitate in a vacuum drying oven at 60 °C to obtain the target conjugated polymer product containing 5% -OH molar content (labeled as PM6-OH 5％ ).

[0079] Example 2

[0080] Prepare a conjugated polymer with a side chain containing 10 mol% -OH crosslinking reaction sites according to the method of Example 1, except that the molar ratio of BDT, BDD and the monomer in the preparation example is 1:0.9:0.1, and the target product is denoted as PM6-OH10％ 。

[0081] Example 3

[0082] Prepare a conjugated polymer with 20 mol% of -OH crosslinking reaction sites in the side chain according to the method of Example 1. The difference is that the molar ratio of BDT, BDD and the monomer prepared in Preparation Example is 1:0.8:0.2, and the target product is denoted as PM6-OH 20％ 。

[0083] Example 4

[0084] This example provides a method for in-situ crosslinking reaction to prepare a conjugated polymer film using PM6-OH prepared in Example 1 5％ as the reaction substrate, and the specific steps are as follows:

[0085] (1) Dissolve PM6-OH 5％ in chlorobenzene;

[0086] (2) After sufficient dissolution, add hexamethylene diisocyanate ( Figure 4 )(-OH and -NCO are in equimolar ratio), and at the same time add a reaction catalyst: dibutyltin dilaurate (the addition amount is 2% of the mass of PM6-OH 5％ );

[0087] (3) After stirring evenly, prepare a film;

[0088] (4) Anneal the film at 80 °C for 20 min to obtain a crosslinked conjugated polymer film (denoted as 2-C-PM6-OH 5％ ).

[0089] Example 5

[0090] Prepare a conjugated polymer film according to the method of Example 4. The difference is that the crosslinking agent is replaced by hexamethylene diisocyanate trimer ( Figure 5 ), and the obtained crosslinked conjugated polymer film is denoted as 3-C-PM6-OH 5％ 。

[0091] Example 6

[0092] Prepare a conjugated polymer film according to the method of Example 4. The difference is that PM6-OH 5％ is replaced by PM6-OH prepared in Example 2 10％ , and the obtained crosslinked conjugated polymer film is denoted as 2-C-PM6-OH 10％ 。

[0093] Example 7

[0094] Prepare the conjugated polymer film according to the method of Example 6, except that the crosslinking agent is replaced with hexamethylene diisocyanate trimer ( Figure 5 ), and the obtained crosslinked conjugated polymer film is denoted as 3-C-PM6-OH 10％ .

[0095] Example 8

[0096] Prepare the conjugated polymer film according to the method of Example 4, except that PM6-OH 5％ is replaced with the PM6-OH prepared in Example 3 20％ , and the obtained crosslinked conjugated polymer film is denoted as 2-C-PM6-OH 20％ .

[0097] Example 9

[0098] Prepare the conjugated polymer film according to the method of Example 8, except that the crosslinking agent is hexamethylene diisocyanate trimer ( Figure 5 ), and the obtained crosslinked conjugated polymer film is denoted as 3-C-PM6-OH 20％ .

[0099] Comparative Example 1

[0100] As Figure 6 shown, a method for synthesizing a conjugated polymer PM6 without -OH groups. The specific steps are as follows:

[0101] (1) Take 423 mg of BDT monomer and 345 mg of BDD monomer (molar ratio 1:1) in a polymerization tube, add 6 mL of toluene, and stir for 10 min until the monomers are completely dissolved;

[0102] (2) Add 11 mg of tetrakis(triphenylphosphine)palladium catalyst;

[0103] (3) Evacuate and refill with nitrogen 10 times, transfer the polymerization tube to an oil bath at 115 °C and react for 72 h;

[0104] (4) After the reaction is completed, precipitate the product in methanol;

[0105] (5) Soxhlet extract the product with methanol, petroleum ether, and dichloromethane in sequence;

[0106] (6) Heat and dissolve the Soxhlet-extracted product in chlorobenzene for 1 h;

[0107] (7) After filtering the solution, precipitate it again in methanol;

[0108] (8) After suction filtration, dry the precipitate in a vacuum drying oven at 60 °C to obtain the conjugated polymer PM6.

[0109] Further, PM6 was fully dissolved in chlorobenzene and then spin-coated into a film using a spin coater, followed by annealing at 80 °C for 20 min to obtain a PM6 polymer film.

[0110] Test Example 1

[0111] The mechanical properties of the polymer films prepared in Examples 4-9 and Comparative Example 1 were tested.

[0112] The specific test method is as follows: The tensile properties of the polymer film were measured using a tensile tester on water. The specific process is as follows: A cleaned glass plate (size specification: 25 mm × 40 mm) was placed in an ultraviolet ozone cleaning machine for hydrophilic treatment. Subsequently, an aqueous solution of sodium polystyrene sulfonate (PSSNa) was spin-coated on the surface of the glass plate, annealed at 100 °C for 5 min, and then the sample solution to be tested was spin-coated on top of the PSSNa and annealed at 80 °C for 10 min to form a sample film of about 120 nm. After covering the film with a PDMS template in the shape of a dog bone, the entire glass substrate was placed in a vacuum plasma cleaning machine for etching to remove all the film not covered by the PDMS template. After the etching was completed, the PDMS template was gently peeled off to obtain a sample film with a standard shape. Utilizing the surface tension of water, the sample film was floated on deionized water and attached to the tensile device for tensile property testing. After processing the measured data, the stress-strain curve of the sample could be obtained.

[0113] Critical onset strain (COS): The strain value (usually expressed as a percentage) corresponding to the first visible crack on the surface or inside of the material during the tensile process, which is the transition point of the material from uniform plastic deformation to local brittle fracture. Corresponding to the strain value at the fracture point on the stress-strain curve.

[0114] Toughness: Characterizes the ability of the material to absorb energy before fracture, which is a comprehensive manifestation of strength and ductility. Its value corresponds to the area enclosed by the stress-strain curve from the origin to the fracture point.

[0115] Compared with Comparative Example 1, the mechanical properties of the conjugated polymer films in Examples 4 and 5 were significantly enhanced. As Figure 7 shown, the critical onset strain (COS) and toughness of the pure PM6 film were 10.44% and 3.03 MJ / m 3 respectively; for the 2-C-PM6-OH 5％ film obtained by in-situ cross-linking reaction in Example 4, the critical onset strain and toughness were increased to 27.41% and 10.13 MJ / m 3 respectively; for the 3-C-PM6-OH 5％ film obtained in Example 5, the mechanical properties were also improved, with a critical onset strain of 28.19% and a toughness of 12.58 MJ / m 3This indicates that for the conjugated polymer thin film obtained through in-situ crosslinking reaction, the tensile property has been significantly improved, and the energy value absorbed when stretched to the breaking point has increased significantly.

[0116] Compared with Comparative Example 1, the mechanical properties of the conjugated polymer thin films in Examples 6 and 7 are further enhanced. As Figure 8 shown, the crack onset strain (COS) and toughness of the pure PM6 thin film are 10.44% and 3.03 MJ / m 3 respectively; for the 2-C-PM6-OH 10％ thin film obtained by in-situ crosslinking reaction in Example 6, the crack onset strain and toughness are greatly improved to 38.69% and 14.05 MJ / m 3 respectively; for the 3-C-PM6-OH 10％ thin film obtained in Example 7, the mechanical properties are even more significantly improved, with the crack onset strain being 45.15% and the toughness reaching 19.19 MJ / m 3 . This indicates that for the conjugated polymer obtained through in-situ crosslinking reaction, the tensile property has been significantly improved, and the energy value absorbed when stretched to the breaking point has increased significantly.

[0117] Compared with Comparative Example 1, the mechanical properties of the conjugated polymer thin film in Example 8 are greatly enhanced. As Figure 9 shown, the crack onset strain (COS) and toughness of the pure PM6 thin film are 10.44% and 3.03 MJ / m 3 respectively; for the 2-C-PM6-OH 20％ thin film obtained by in-situ crosslinking reaction in Example 8, the crack onset strain and toughness are greatly improved to 59.84% and 22.77 MJ / m 3 , the elongation at break is increased by 5.7 times, and the toughness is increased by 7.5 times; for the conjugated polymer thin film 3-C-PM6-OH 20％ obtained in Example 9, the mechanical properties are not significantly improved, with the crack onset strain being 29.19% and the toughness reaching 10.07 MJ / m 3 . Analyzing the reason, it may be that due to the excessive crosslinking density, the movement ability of the polymer chains is restricted, and the segments cannot disperse stress by slipping. Therefore, it is necessary to control the crosslinking density well to achieve a balance between rigidity and toughness and optimize the material properties.

[0118] The above examples indicate that for the conjugated polymer obtained through in-situ crosslinking reaction, the tensile property has been significantly improved, and on the basis of ensuring solution processability, the mechanical properties have been greatly improved.

[0119] Example 10

[0120] The present invention provides a method using 2-C-PM6-OH in Example 4 5％As an example of a rigid organic solar cell applied as a donor material to the light absorption layer, the specific steps are as follows:

[0121] Step 1: Preparation of the hole transport layer. Configure 2PACz into an ethanol solution with a concentration of 0.2 mg / mL. After mixing the solution evenly, use a spin coater to spin-coat a film on the ITO / glass bottom electrode, and then anneal it at 80 °C for 3 min to obtain the hole transport layer.

[0122] Step 2: Preparation of the light absorption layer. Add PM6-OH 5％ and BTP-eC9 to a chloroform solution of 1,3-dibromo-5-chlorobenzene with a concentration of 16.5 mg / mL at a mass ratio of 1:1.2 to form a mixed solution with a concentration of 28 mg / mL. Place it on a hot plate at 80 °C and heat it. After the monomers are completely dissolved, add hexamethylene diisocyanate (-OH and -NCO are in equimolar ratio) and a catalyst: dibutyltin dilaurate (the addition amount is 2% of the mass of PM6-OH 5％ to the above mixed solution, stir for 2 min to mix evenly, use a spin coater to spin-coat a film on the hole transport layer, and then anneal it at 80 °C for 20 min to obtain a light absorption layer with a thickness of about 100 nm.

[0123] Step 3: Preparation of the electron transport layer. Dissolve PDINN in a methanol solvent with a concentration of 1 mg / mL, and use a spin coater to spin-coat a film on the light absorption layer to form an electron transport layer with a thickness of about 5 nm.

[0124] Step 4: Preparation of the top electrode. Vacuum deposit metallic silver onto the above electron transport layer to form a top electrode with a thickness of about 80 nm, completing the preparation of the organic solar cell (labeled as 2-C-PM6-OH 5％ :BTP-eC9).

[0125] Comparative Example 2

[0126] Prepare a rigid organic solar cell according to the method of Example 10, except that PM6-OH 5％ in the second step is replaced with the conjugated polymer PM6 of Comparative Example 1 (labeled as PM6:BTP-eC9).

[0127] Figure 10 Figure 30 shows the current density-voltage curves of the organic solar cells prepared in Example 10 and Comparative Example 2. The solar cell prepared in Example 10 has a higher power conversion efficiency of 17.59%, and the PM6:BTP-eC9 system of Comparative Example 2 is 17.51%. It shows that the material structure designed by the in-situ crosslinking strategy can not only improve the mechanical properties of the conjugated polymer, but also maintain and even optimize the electrical properties.

[0128] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for preparing a conjugated polymer film, characterized in that: The method comprises the following steps: (1) in the presence of a first solvent and a first catalyst, subjecting (4,8-bis(5-(2-ethylhexyl)-4-fluorothienyl)benzo[1,2-b:4,5-b']dithienyl)bis(trimethyltinyl), 1,3-bis(5-bromothien-2-yl)-5,7-bis(2-ethylhexyl)benzo[1,2-c:4,5-c']dithiophene-4,8-dione and a monomer represented by formula I to a ternary copolymerization reaction to obtain a ternary conjugated polymer; (2) blending the ternary conjugated polymer obtained in step (1), the second solvent, the cross-linking agent and the second catalyst to form a film, and annealing to obtain the conjugated polymer film; 2. The method according to claim 1, wherein: The first solvent is toluene; Preferably, the first catalyst is tetrakis(triphenylphosphine)palladium; Preferably, the first catalyst is used in an amount of 1-5 mol %, preferably 2 mol %, of (4,8-bis(5-(2-ethylhexyl)-4-fluorothienyl)benzo[1,2-b:4,5-b']dithienyl)bis(trimethyltinyl).

3. The method according to claim 1 or 2, wherein: In step (1), the molar ratio of (4,8-bis(5-(2-ethylhexyl)-4-fluorothienyl)benzo[1,2-b:4,5-b']dithienyl)bis(trimethyltinyl), 1,3-bis(5-bromothien-2-yl)-5,7-bis(2-ethylhexyl)benzo[1,2-c:4,5-c']dithiophene-4,8-dione and the monomer represented by formula I is 1:0.8-0.95:0.05-0.2, preferably 1:0.9:0.

1.

4. The method according to any one of claims 1 to 3, wherein: The second solvent is selected from at least one of chlorobenzene, toluene and chloroform; Preferably, the second catalyst is selected from at least one of dibutyltin dilaurate, stannous octoate, bismuth isooctanoate and triethylenediamine; Preferably, the amount of the second catalyst used is 1-5% of the mass of the ternary conjugated polymer obtained in step (1), preferably 2%.

5. The method according to any one of claims 1 to 4, wherein: The cross-linking agent contains a functional group capable of undergoing a cross-linking reaction with a hydroxyl group, preferably at least one selected from a methacrylate group, a carboxyl group, an epoxy group and an isocyanate group, preferably an isocyanate group; Preferably, the number of functional groups in the cross-linking agent is at least 2; Preferably, the molar ratio of the functional groups in the cross-linking agent to the hydroxyl groups in the monomer represented by formula I is 1:1; Preferably, the cross-linking agent is selected from at least one of hexamethylene diisocyanate, hexamethylene diisocyanate trimer, L-lysine triisocyanate and diphenylmethane diisocyanate.

6. The method according to any one of claims 1 to 5, wherein: The synthesis method of the monomer shown in formula I comprises: reacting 2,5-dibromothiophene-3-carboxylic acid and dodecanediol in a protective atmosphere to obtain the monomer shown in formula I; Preferably, the solvent of the reaction is a mixed solvent of dichloromethane and dimethyl sulfoxide; Preferably, the catalyst of the reaction is 4-dimethylaminopyridine (DMAP) and N,N-dicyclohexylcarbodiimide (DCC); Preferably, the protective atmosphere gas is nitrogen; Preferably, the reaction conditions include: room temperature; time is 32h; Preferably, the product of the reaction is subjected to extraction, drying, column chromatography and recrystallization to obtain the monomer represented by formula I.

7. The method according to any one of claims 1 to 6, wherein: The conditions for the terpolymerization reaction in step (1) include: protective atmosphere; temperature of 110-130° C., preferably 115° C.; time of 48-96 h, preferably 72 h; Preferably, the protective atmosphere gas is nitrogen; Preferably, the annealing conditions in step (2) include: a temperature of 80-100° C., preferably 80° C.; and a time of 10-30 min, preferably 20 min.

8. The conjugated polymer film obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the conjugated polymer film according to claim 8 in the preparation of organic electronic devices; Preferably, the conjugated polymer film serves as a light absorbing layer; Preferably, the organic electronic device is an organic solar cell.

10. An organic solar cell comprising the conjugated polymer film of claim 8 as a light absorbing layer.

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