Conjugated polymer thin films, methods of making and using the same

Abstract

The application relates to the field of photoelectric technology, and discloses a conjugated polymer thin film and a preparation method and application thereof. In the presence of a first solvent and a first catalyst, ternary copolymerization is carried out on (4,8-bis(5-(2-ethylhexyl)-4-fluorothiophenyl)benzo[1,2-b:4,5-b']dithiophenyl)bis(trimethyl tin), 1,3-bis(5-bromothiophene-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, so as to obtain a ternary conjugated polymer; the obtained ternary conjugated polymer, a second solvent, a crosslinking agent and a second catalyst are blended to form a film, and annealing is carried out to obtain the conjugated polymer thin film. The conjugated polymer thin film can be used as a light absorption layer to prepare an organic electronic device. The conjugated polymer thin film obtained by the method has significantly improved mechanical performance on the basis of ensuring photoelectric performance; the in-situ crosslinking strategy is adopted, solution processing performance is ensured, the operation is simple, the controllability of the polymer structure is high, and batch repeatability is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optoelectronic technology, in particular to a conjugated polymer thin film and a preparation method and application thereof. BACKGROUND

[0002] Conjugated polymers are a class of high molecular materials with π-π conjugated main chain structure, which have excellent photoelectric properties (such as high carrier mobility, adjustable optical band gap) and good solution processing property, and 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 high molecular materials, conjugated polymers usually exhibit poor mechanical properties, such as brittleness, low ductility, insufficient tensile strength, etc. These defects in mechanical properties seriously limit their practical application in flexible devices, especially in scenarios requiring repeated deformation or bearing mechanical stress. Therefore, improving the mechanical properties of conjugated polymers has become an important research direction in the field of material science in recent years.

[0003] The mechanical properties of conjugated polymers are closely related to their molecular structure, interchain interaction, crystallinity and film morphology, etc. Traditional conjugated polymers usually have a rigid main chain structure, and there is strong π-π interaction between molecular chains, which is beneficial to charge transport, but also leads to increased brittleness. In order to improve their mechanical properties, researchers have carried out in-depth research from multiple angles such as molecular design, microstructure regulation and composite material preparation. For example, conjugated polymers can be physically blended with elastomers or other high molecular materials to improve their mechanical properties, however, physical blending may cause phase separation, thereby affecting 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, the introduction of flexible side chains may reduce the charge transport capacity, and too long side chains may cause disordered molecular packing, affecting crystallinity and photoelectric properties, etc.

[0004] In addition, cross-linking strategies can also be used, such as polymerization followed by cross-linking (introducing cross-linkable groups in the conjugated semiconductor side chain) or direct polymerization cross-linking (directly introducing cross-linking structure during the preparation of conjugated polymers) to construct light absorbing layers containing cross-linking structure, inhibit the movement and sliding of molecular chains, and enhance the intermolecular interaction force, thereby improving the mechanical properties of the light absorbing layer. However, existing cross-linking strategies have problems such as complex preparation process, difficulty in accurately controlling the structure of the polymer, poor batch repeatability, risk of decomposition induced by photo-crosslinking, need to strictly control the molecular weight to ensure solution processing property, and potential negative impact on photoelectric properties, etc.

[0005] Therefore, it is necessary to develop a new conjugated polymer cross-linking strategy to simplify the preparation process, improve the controllability and batch repeatability of the structure, and ensure the solution processing performance, so as to greatly improve the mechanical properties without losing the photoelectric properties as much as possible. SUMMARY

[0006] The present application aims to overcome the problems existing in the prior art and provide a conjugated polymer thin film, a preparation method and application thereof.

[0007] To achieve the above-mentioned purpose, the first aspect of the present application provides a preparation method of a conjugated polymer thin film, wherein the method comprises the following steps:

[0008] (1) ternary copolymerization of (4,8-bis(5-(2-ethylhexyl)-4-fluorothiophenyl)benzo[1,2-b:4,5-b']dithiophenyl)bis(trimethyltin), 1,3-bis(5-bromothiophene-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 in the presence of a first solvent and a first catalyst to obtain a ternary conjugated polymer;

[0009] (2) blending the ternary conjugated polymer obtained in step (1), a second solvent, a cross-linking agent and a second catalyst to form a film, and annealing to obtain the conjugated polymer thin film;

[0010]

[0011]

[0012] The second aspect of the present application provides a conjugated polymer thin film obtained by the preparation method according to the first aspect.

[0013] The third aspect of the present application provides an application of the conjugated polymer thin film according to the second aspect in preparing an organic electronic device.

[0014] The fourth aspect of the present application provides an organic solar cell comprising the conjugated polymer thin film according to the second aspect as a light absorbing layer.

[0015] Through the above technical solution, the present application has the following beneficial technical effects:

[0016] (1) The conjugated polymer thin film obtained by the method of the present application has significantly improved mechanical properties while ensuring photoelectric properties;

[0017] (2) The in-situ cross-linking strategy adopted by the present application ensures solution processing performance, is simple to operate, and has high controllability and batch repeatability of the polymer structure. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 This is the synthetic route for the monomer of formula I in the preparation example of the present invention.

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

[0020] Figure 3 This 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 this 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 this invention.

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

[0024] Figure 7 These are the stress-strain curves of the conjugated polymer films in Examples 4 and 5 and Comparative Example 1.

[0025] Figure 8 These are the stress-strain curves of the conjugated polymer films in Examples 6 and 7 and Comparative Example 1.

[0026] Figure 9 These are the stress-strain curves of the conjugated polymer films in Examples 8 and 9 and Comparative Example 1.

[0027] Figure 10 These are the current density-voltage curves of the organic solar cells prepared in Example 10 and Comparative Example 2. Detailed Implementation

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

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

[0030] (1) ternary copolymerization of (4,8-bis(5-(2-ethylhexyl)-4-fluorothienyl)benzo[1,2-b:4,5-b']dithiophenyl)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 the monomer shown in formula I in the presence of a first solvent and a first catalyst to obtain a ternary conjugated polymer;

[0031] (2) blending the ternary conjugated polymer obtained in step (1), a second solvent, a crosslinking agent and a second catalyst to form a film and annealing to obtain the conjugated polymer film;

[0032]

[0033] The monomer shown in formula I (which can be named as 2,5-dibromothiophene-3-methyl ester dodecanol) is added in the preparation of the conjugated polymer, so that the solution processability can be ensured by in-situ crosslinking (crosslinking after spin coating); the prepared conjugated polymer film not only improves the mechanical properties (such as tensile properties), but also can maintain or even improve the photoelectric properties when used in electronic devices.

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

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

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

[0037] In step (1) of the present application, the molar ratio of (4,8-bis(5-(2-ethylhexyl)-4-fluorothienyl)benzo[1,2-b:4,5-b']dithiophenyl)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 shown in formula I is 1:0.8-0.95:0.05-0.2, preferably 1:0.9:0.1. In the present application, the molar content of the monomer shown in formula I is controlled in a specific range, which can ensure the mechanical properties and photoelectric properties of the film at the same time.

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

[0039] In some embodiments of the present application, 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 application, the second catalyst is used in an amount of 1-5%, preferably 2%, of the mass of the terpolymer obtained in step (1).

[0041] In some embodiments of the present application, the crosslinking agent comprises a functional group capable of crosslinking reaction with hydroxyl groups, preferably at least one selected from the group consisting of methacrylate, carboxyl, epoxy, isocyanate, preferably isocyanate.

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

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

[0044] In some embodiments of the present application, 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 application, the method for synthesizing the monomer of formula I comprises: reacting 2,5-dibromothiophene-3-carboxylic acid and dodecanediol in a protective atmosphere to obtain the monomer of formula I.

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

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

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

[0049] In some embodiments of the present application, the reaction conditions include: room temperature; and a time of 32 h.

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

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

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

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

[0054] The second aspect of the present application provides a conjugated polymer thin film prepared by the method according to the first aspect.

[0055] The third aspect of the present application provides the use of the conjugated polymer thin film according to the second aspect in the preparation of an organic electronic device.

[0056] In some embodiments of the present application, the conjugated polymer thin film is used as a light-absorbing layer.

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

[0058] The fourth aspect of the present application provides an organic solar cell comprising the conjugated polymer thin film according to the second aspect as a light-absorbing layer.

[0059] The light-absorbing layer further comprises a small molecule acceptor.

[0060] The present application will be described in detail below by way of examples.

[0061] In the following examples and comparative examples, the specific conditions not specified are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, if not specified, are conventional products that can be obtained by market purchase.

[0062] Preparation Example

[0063] The present preparation example provides a synthesis method of a monomer of formula I containing -OH side chain. The reaction process is as shown in Figure 1 The specific steps are as follows:

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

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

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

[0067] (4) The obtained liquid was recrystallized three times using petroleum ether to obtain the target product: the monomer represented by Formula I.

[0068] The proton nuclear magnetic resonance spectrum of the monomer represented by Formula I is shown in Figure 2 . 1 H NMR (400 MHz, CDC13) 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 shown in Figure 3 , this example provides a method for preparing a conjugated polymer having 5% molar content of -OH groups in the side chain. 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 (molar ratio of the three monomers is 1:0.95:0.05) into 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) Pump nitrogen 10 times, transfer the polymerization tube to a 115°C oil bath, and react for 72 h;

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

[0075] (5) The product is sequentially subjected to Soxhlet extraction using methanol, petroleum ether, and dichloromethane;

[0076] (6) The extracted product is dissolved in chlorobenzene for 1 h;

[0077] (7) The solution is filtered and then settled in methanol again;

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

[0079] Example 2

[0080] A conjugated polymer having 10% molar content of -OH crosslinking reaction sites in the side chain is prepared according to the method of Example 1, except that the molar ratio of BDT, BDD, and the monomer of the preparation example is 1:0.9:0.1, and the target product is labeled as PM6-OH.10％ .

[0081] Example 3

[0082] The conjugated polymer with 20% molar content of -OH crosslinking reaction sites in the side chain was prepared according to the method of Example 1, except that the molar ratio of BDT, BDD and the monomer of Preparation Example was 1:0.8:0.2, and the target product was recorded as PM6-OH 20％ .

[0083] Example 4

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

[0085] (1) PM6-OH 5％ was dissolved with chlorobenzene;

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

[0087] (3) After stirring uniformly, a film was prepared;

[0088] (4) The film was annealed at 80°C for 20 min, and a crosslinked conjugated polymer film (recorded as 2-C-PM6-OH 5％ ) was obtained.

[0089] Example 5

[0090] The conjugated polymer film was prepared according to the method of Example 4, except that the crosslinking agent was replaced by hexamethylene diisocyanate trimer Figure 5 , and the obtained crosslinked conjugated polymer film was recorded as 3-C-PM6-OH 5％ .

[0091] Example 6

[0092] The conjugated polymer film was prepared according to the method of Example 4, except that PM6-OH 5％ was replaced by PM6-OH 10％ prepared in Example 2, and the obtained crosslinked conjugated polymer film was recorded as 2-C-PM6-OH 10％ .

[0093] Example 7

[0094] A conjugated polymer thin film was prepared according to the method of Example 6, except that the crosslinking agent was replaced by hexamethylene diisocyanate trimer (HDI trimer) Figure 5 , and the obtained crosslinked conjugated polymer thin film was recorded as 3-C-PM6-OH 10％ .

[0095] Example 8

[0096] A conjugated polymer thin film was prepared according to the method of Example 4, except that PM6-OH 5％ was replaced by PM6-OH 20％ prepared in Example 3, and the obtained crosslinked conjugated polymer thin film was recorded as 2-C-PM6-OH 20％ .

[0097] Example 9

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

[0099] Comparative Example 1

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

[0101] (1) 423 mg of BDT monomer and 345 mg of BDD monomer (molar ratio of 1:1) were taken in a polymerization tube, 6 mL of toluene was added, and stirred for 10 min until the monomers were completely dissolved;

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

[0103] (3) Nitrogen was pumped for 10 times, and the polymerization tube was transferred to an oil bath at 115°C for reaction for 72 h;

[0104] (4) After the reaction was completed, the product was settled in methanol;

[0105] (5) The product was sequentially subjected to Soxhlet extraction with methanol, petroleum ether and dichloromethane;

[0106] (6) The extracted product was dissolved with chlorobenzene for 1 h;

[0107] (7) The solution was filtered and then settled in methanol again;

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

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

[0110] Test Example 1

[0111] The polymer films prepared in Examples 4-9 and Comparative Example 1 were subjected to mechanical property tests.

[0112] The specific testing method is as follows: The tensile properties of the polymer film were determined using a water-based tensile testing apparatus. The specific process is as follows: A cleaned glass plate (size: 25mm × 40mm) was placed in a UV ozone cleaner for hydrophilic treatment. Then, a layer of sodium polystyrene sulfonate (PSSNa) aqueous solution was spin-coated onto the glass plate surface and annealed at 100℃ for 5 minutes. The sample solution to be tested was then spin-coated onto the PSSNa layer and annealed at 80℃ for 10 minutes, forming a sample film of approximately 120nm. After covering the film with a dog-bone-shaped PDMS template, the entire glass substrate was placed in a vacuum plasma cleaner for etching, removing all film areas not covered by the PDMS template. After etching, the PDMS template was gently peeled off to obtain a standard-shaped sample film. Utilizing the surface tension of water, the sample film was floated on deionized water and attached to the tensile testing apparatus for tensile property testing. The measured data were processed to obtain the stress-strain curve of the sample.

[0113] Fracture initiation strain (COS): The strain value (usually expressed as a percentage) corresponding to the first visible crack appearing on the surface or inside a material during tensile testing. It represents the transition point from uniform plastic deformation to localized brittle fracture. It corresponds to the strain value at the fracture point on the stress-strain curve.

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

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

[0116] Compared to Comparative Example 1, the mechanical properties of the conjugated polymer films in Examples 6 and 7 were further enhanced. For example... Figure 8 As shown, the fracture initiation strain (COS) and toughness of the pure PM6 film are 10.44% and 3.03 MJ / m, respectively. 3 Example 6: 2-C-PM6-OH obtained by in-situ crosslinking reaction. 10％ The fracture initiation strain and toughness of the thin film were significantly improved to 38.69% and 14.05 MJ / m, respectively. 3 ; 3-C-PM6-OH obtained in Example 7 10％ The thin film exhibits a more significant improvement in mechanical properties, with a fracture initiation strain of 45.15% and a toughness reaching 19.19 MJ / m. 3 This indicates that the conjugated polymer obtained through in-situ crosslinking reaction has significantly improved tensile properties, and the energy absorbed when stretched to the breaking point is significantly increased.

[0117] Compared to Comparative Example 1, the mechanical properties of the conjugated polymer film in Example 8 were significantly enhanced. For example... Figure 9 As shown, the fracture initiation strain (COS) and toughness of the pure PM6 film are 10.44% and 3.03 MJ / m, respectively. 3 Example 8: 2-C-PM6-OH obtained by in-situ crosslinking reaction. 20％ The fracture initiation strain and toughness of the thin film were significantly improved to 59.84% and 22.77 MJ / m, respectively. 3 The elongation at break increased by 5.7 times, and the toughness increased by 7.5 times; while the conjugated polymer film 3-C-PM6-OH obtained in Example 9... 20％ The improvement in mechanical properties was not significant, with a fracture initiation strain of 29.19%, while the toughness reached 10.07 MJ / m. 3 The reason for this may be that excessive crosslinking density restricts the mobility of polymer chains, preventing chain segments from dispersing stress through slippage. Therefore, it is necessary to control the crosslinking density to achieve a balance between rigidity and toughness, thus optimizing material properties.

[0118] The above examples demonstrate that conjugated polymers obtained through in-situ crosslinking reactions exhibit significantly improved tensile properties and substantially enhanced mechanical properties while maintaining solution processing performance.

[0119] Example 10

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

[0121] First step: preparation of the hole transport layer. 2PACz is configured into an ethanol solution of 0.2 mg / mL, and after the solution is mixed uniformly, it is spin-coated onto an ITO / glass bottom electrode using a spin coater, and then annealed at 80°C for 3 min to obtain the hole transport layer.

[0122] Second step: preparation of the light-absorbing layer. PM6-OH 5％ and BTP-eC9 are added to a chloroform solution of 1,3-dibromo-5-chlorobenzene at a mass ratio of 1:1.2 to form a mixed solution with a concentration of 28 mg / mL, which is heated on a hot stage at 80°C. After the monomers are completely dissolved, hexamethylene diisocyanate (-OH and -NCO are in equimolar ratio) and a catalyst, dibutyltin dilaurate (added in an amount of 2% of the mass of PM6-OH 5％ ), are added to the mixed solution, which is stirred for 2 min to mix uniformly, and then spin-coated onto the hole transport layer using a spin coater, followed by annealing at 80°C for 20 min to obtain a light-absorbing layer with a thickness of about 100 nm.

[0123] Third step: preparation of the electron transport layer. PDINN is dissolved in a methanol solvent to a concentration of 1 mg / mL, and spin-coated onto the light-absorbing layer using a spin coater to form an electron transport layer with a thickness of about 5 nm.

[0124] Fourth step: preparation of the top electrode. Metal silver is vacuum evaporated 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 2-C-PM6-OH 5％ :BTP-eC9).

[0125] Comparative Example 2

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

[0127] Figure 10 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 photoelectric conversion efficiency of 17.59%, and the PM6:BTP-eC9 system of Comparative Example 2 is 17.51%. This shows that the material structure designed by the in-situ crosslinking strategy not only improves the mechanical properties of the conjugated polymer, but also maintains and even optimizes the electrical properties.

[0128] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A method for preparing a conjugated polymer film, characterized in that, The method includes the following steps: (1) In the presence of a first solvent and a first catalyst, (4,8-bis(5-(2-ethylhexyl)-4-fluorothiophenyl)benzo[1,2-b:4,5-b']dithiophenyl)bis(trimethyltinyl), 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 shown in Formula I undergo a ternary copolymerization reaction to obtain a ternary copolymer. The conjugated polymer; wherein the molar ratio of (4,8-bis(5-(2-ethylhexyl)-4-fluorothiophenyl)benzo[1,2-b:4,5-b']dithiophenyl)bis(trimethyltinyl), 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 shown in Formula I is 1:0.8-0.95:0.05-0.2; (2) The ternary conjugated polymer obtained in step (1), the second solvent, the crosslinking agent and the second catalyst are blended and then formed into a film, and annealed to obtain the conjugated polymer film; wherein the crosslinking agent is selected from at least one of hexamethylene diisocyanate, hexamethylene diisocyanate trimer, L-lysine triisocyanate and diphenylmethane diisocyanate; Formula I.

2. The method according to claim 1, wherein, The first solvent is toluene; And / or, the first catalyst is tetra(triphenylphosphine)palladium; And / or, the amount of the first catalyst is 1-5 mol of (4,8-bis(5-(2-ethylhexyl)-4-fluorothiophene)benzo[1,2-b:4,5-b']dithiophene)bis(trimethyltinyl).

3. The method according to claim 1, wherein, The amount of the first catalyst is 2 mol of (4,8-bis(5-(2-ethylhexyl)-4-fluorothiophene)benzo[1,2-b:4,5-b']dithiophene)bis(trimethyltinyl).

4. The method according to claim 1 or 2, wherein, In step (1), the molar ratio of (4,8-bis(5-(2-ethylhexyl)-4-fluorothiophenyl)benzo[1,2-b:4,5-b']dithiophenyl)bis(trimethyltinyl), 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 shown in Formula I is 1:0.9:0.

1.

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

6. The method according to any one of claims 1-3, wherein, The amount of the second catalyst is 2% of the mass of the ternary conjugated polymer obtained in step (1).

7. The method according to any one of claims 1-3, wherein, The molar ratio of the functional groups in the crosslinking agent to the hydroxyl groups in the monomer shown in Formula I is 1:

1.

8. The method according to any one of claims 1-3, wherein, The method for synthesizing the monomer shown in Formula I includes reacting 2,5-dibromothiophene-3-carboxylic acid and dodecanediol in a protective atmosphere to obtain the monomer shown in Formula I.

9. The method according to claim 8, wherein, The solvent for the reaction is a mixture of dichloromethane and dimethyl sulfoxide; And / or, the catalyst for the reaction is 4-dimethylaminopyridine (DMAP) and N,N-dicyclohexylcarbodiimide (DCC). And / or, the protective atmosphere is nitrogen; And / or, the reaction conditions include: room temperature; time of 32 h; And / or, the product of the reaction is extracted, dried, subjected to column chromatography, and recrystallized to obtain the monomer shown in Formula I.

10. The method according to any one of claims 1-3, wherein, The conditions for the ternary copolymerization reaction described in step (1) include: a protective atmosphere; a temperature of 110-130 °C; and a time of 48-96 h. And / or, the annealing conditions described in step (2) include: a temperature of 80-100 °C and a time of 10-30 min.

11. The method according to claim 10, wherein, The protective atmosphere is made of nitrogen. And / or, the annealing conditions described in step (2) include: a temperature of 80 °C and a time of 20 min.

12. The conjugated polymer film obtained by the preparation method according to any one of claims 1-11.

13. The application of the conjugated polymer film of claim 12 in the preparation of organic electronic devices.

14. The application according to claim 13, wherein, The conjugated polymer film serves as a light-absorbing layer; And / or, the organic electronic device is an organic solar cell.

15. An organic solar cell comprising the conjugated polymer film of claim 12 as a light-absorbing layer.

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