A dithienylthiazolothiazole polymer based on sulfane chain substitution, and its preparation method and application

Abstract

The present invention provides a thiolane-chain-substituted dithienylthiazolothiazole polymer, a preparation method thereof, and an application thereof. A dithienylthiazolothiazole (STTz) unit containing an alkylthio-chain substitution and another benzodithiophene (BDT) unit are connected by a Stille coupling polymerization method to obtain STTz-based organic polymers, namely, polymer PBF-STTz1 and PBSiCl-STTz1 based on 2,5-bis(4-((2-butyl octyl)thio)thiophen-2-yl)thiazolo[5,4-d]thiazole (STTz). The thiolane-chain-substituted dithienylthiazolothiazole unit provided by the present invention has the advantages of simple structure, good planarity, etc., and is suitable for constructing conjugated polymers with excellent properties, and can be applied to donor materials of organic solar cells. For an organic solar cell prepared with such a polymer as the donor material and Y6 as the acceptor material, an energy conversion efficiency value of 6.51-10.34% can be obtained without annealing and additive optimization.

Description

Technical Field

[0001] The present invention relates to the technical field of organic optoelectronic functional materials, and particularly relates to a dithienylthiazolothiazole polymer substituted with a sulfane chain, a preparation method thereof, and an application thereof. Background Art

[0002] Benzodithiophene and thiazolothiazole (PBDT-TTz) polymers have shown great potential in the field of organic solar cells [Qinqin Shi, Haijun Fan, Yao Liu, et al. Synthesis of copolymers based on thiazolothiazole and their applications in polymer solar cells [J]. J Phys Chem C 2010, 114:16843–16848; Miao Yang, Bo Peng, Bo Liu, et al. Synthesis and photovoltaic properties of copolymers from benzodithiophene and thiazole [J]. J Phys Chem C, 2010, 114:17989–17994.]. After using alkylthiophene-substituted benzodithiophene units, the photovoltaic performance of these polymers has been greatly improved. Blended with non-fullerene acceptors, a maximum power conversion efficiency of 11.7% has been achieved [Bing Guo, Xia Guo, Wanbin Li, et al. A wide-bandgap conjugated polymer for highly efficient inverted single and tandem polymer solar cells [J]. J Mater Chem A, 2016, 4:13251]. Subsequently, there have been more and more reports on the structural modification of benzodithiophene and thiazolothiazole (PBDT-TTz) polymers. For example, it has been reported that fluorine atoms are introduced into the polymer backbone, and a benzodithiophene and thiazolothiazole (PBDT-TTz) polymer PB[N][F] is synthesized, achieving a power conversion efficiency of 14.4% [Zhixiong Gao, Jiale Chen, Shengjian Liu, et al. Synergistic effects of polymer donor backbone fluorination and nitrogenation translate into efficient non-fullerene bulk-heterojunction polymer solar cells [J]. ACS Appl Mater Interfaces 2020, 12:9545-9554.].Professor Peng Qiang's research group introduced two unconventional types of side chains, carboxylate and carbamate, at the thiophene π-bridge of thiazolothiazole-based polymer donor materials, and synthesized new polymers PTzTz-C and PTzTz-N with an energy conversion efficiency as high as 18.76% [Jie Tang, Chentong Liao, Yuwei Duan, et al. Wideband-gap polymer donors functionalized with unconventional carbamate sidechains for polymer solar cells [J]. Angew Chem Int Ed, 2022, 61(50): e202213252]. Based on the alkanethiol-chain-substituted dithienylthiazolothiazole unit, which is an important electron donor unit, there has never been a report on polymer donor materials formed with BDT units. Summary of the Invention

[0003] In the technical solution of the present invention, the purpose is to provide a polymer containing alkanethiol-chain-substituted dithienylthiazolothiazole, its preparation method and application. This organic polymer photovoltaic material is synthesized by the Stille coupling polymerization method of alkanethiol-chain-substituted dithienylthiazolothiazole units and benzodithiophene derivative units, and can be used as a polymer donor material for preparing organic solar cells. The organic solar cells prepared by blending with the non-fullerene acceptor Y6 can reach an energy conversion efficiency value of 6.51 - 10.34%.

[0004] To achieve the above purpose, the present invention first provides a polymer based on alkanethiol-chain-substituted dithienylthiazolothiazole, and the polymer contains a 2,5-bis(4-((2-butyl octyl)thio)thiophen-2-yl)thiazolo[5,4-d]thiazole structural unit, and its structural formula is shown as Formula I or Formula II below:

[0005]

[0006] Where n is a positive integer greater than 1.

[0007] Based on a general inventive concept, the present invention also provides a preparation method of a polymer based on alkanethiol-chain-substituted dithienylthiazolothiazole, including the following steps: reacting the compound STTz-Br with 4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)bis(trimethylstannane) and (2,6-bis(trimethylstannanyl)benzo[1,2-b:4,5-b']dithiophene-4,8-diyl)bis(3-chlorothiophene-5,2-diyl))bis(tripropylsilane) through a Stille coupling polymerization reaction;

[0008] The structure of the compound STTz-Br is shown in the following formula III:

[0009]

[0010] Preferably, the reaction temperature of the Stille coupling polymerization is 110 °C and the reaction time is 24 h.

[0011] Preferably, the synthesis method of the compound STTz-Br comprises the following steps:

[0012] S1. Using 2-butyl octan-1-ol as a starting material, reacting with triphenylphosphine and N-bromosuccinimide to obtain a compound a shown in formula IV;

[0013] S2. Reacting the compound a with thiourea and ethanol in an alkaline environment to obtain a compound b shown in formula V;

[0014] S3. Catalytically reacting the compound b and 4-bromothiophene-2-carbaldehyde with tetramethylethylenediamine in toluene to obtain a compound c shown in formula VI;

[0015] S4. Condensing the compound c with dithiooxamide in N,N-dimethylformamide to obtain a compound d shown in formula VII;

[0016] S5. Reacting the compound d with N-bromosuccinimide in a mixed solution of chloroform and acetic acid to obtain the compound STTz-Br shown in formula III;

[0017]

[0018] Preferably, in the step S1, the molar ratio of 2-butyl octan-1-ol to N-bromosuccinimide is 1:1 to 2, and the molar ratio of 2-butyl octan-1-ol to triphenylphosphine is 1:1 to 2.

[0019] Preferably, 100 - 200 ml of dichloromethane is further added in the step S1.

[0020] Preferably, in the step S2, the molar ratio of the compound a to thiourea is 1:1 to 2, and the solution used in the alkaline environment is NaOH.

[0021] Preferably, the volume of the ethanol is 50 - 100 ml.

[0022] Preferably, the catalyst for the catalytic reaction in the step S3 is tris(dibenzylideneacetone)dipalladium and 1,1-bis(diphenylphosphino)ferrocene, and the molar ratio of tris(dibenzylideneacetone)dipalladium to 1,1-bis(diphenylphosphino)ferrocene is 1:2 to 2.5.

[0023] Preferably, in the step S4, the molar ratio of compound c to dithiooxamide is 3 to 3.5:1. The volume of the N,N-dimethylformamide is 100 to 120 ml.

[0024] Preferably, in the step S5, the molar ratio of compound d to N-bromosuccinimide is 1:2 to 2.5, and the volume ratio of chloroform to acetic acid is 2 to 2.5:1.

[0025] Based on a general inventive concept, the present invention also provides an application of a dithienylthiazolothiazole polymer substituted with a thiolane chain in the preparation of an organic solar cell.

[0026] Compared with the prior art, the polymer based on dithienylthiazolothiazole substituted with an alkylthio chain developed by the present invention has the following advantages:

[0027] 1. The polymer based on dithienylthiazolothiazole substituted with an alkylthio chain provided by the present invention introduces an alkylthio side chain at the 3-position of the thiophene, and polymerizes with benzodithiophene units containing fluorine atoms, silyl groups, and chlorine atoms respectively. Due to the introduction of the alkylthio side chain, a certain electron density is provided to the conjugated polymer main chain, and a non-covalent bond interaction can be formed between the sulfur atom and the heteroatom on the donor unit, improving the molecular planarity and enhancing the intermolecular force, constructing a conjugated polymer with good planarity. The interaction between the sulfur atom and the heteroatom on the donor unit existing in the molecule is beneficial to enhancing the intramolecular and intermolecular interactions, reducing the intermolecular packing distance, promoting the ordered arrangement of the polymer when forming a semiconductor thin film, and thus improving the charge transport performance;

[0028] 2. The polymer provided by the present invention has appropriate HOMO and LUMO energy levels, as well as an appropriate optical band gap and good carrier transport ability. The electron-donating side chain alkylthio chain in the polymer has a stronger electron-donating ability, which can extend the absorption and reduce the optical band gap. And due to the empty d orbital of the sulfur atom, it has π-electron-withdrawing properties, which can cooperate with F atoms and Cl atoms to effectively reduce the HOMO energy level of the donor material and improve its open-circuit voltage (V oc ) and short-circuit current value (J sc ), and thus improve the energy conversion efficiency (PCE);

[0029] 3. The polymer can be widely used in the preparation of organic solar cells. Using the polymer based on the thiazolothiazole unit with a sulfur-containing alkyl side group provided by the present invention as a donor material, the organic solar cell prepared by blending with the non-fullerene acceptor Y6 can reach a device photoenergy conversion efficiency of 6.51 to 10.34% without annealing and additive optimization;

[0030] 4. The polymer containing alkane thiol chain-substituted dithienylthiazolothiazole provided by the present invention is easily soluble in organic solvents such as dichloromethane and chloroform. Therefore, a spin coating method can be used to prepare a thin film for a solar cell.

[0031] 5. The polymer provided by the present invention has the advantages of a simple synthesis route, easy purification, low cost, etc., and has good application prospects. Description of the Drawings

[0032] Figure 1 1H NMR spectrum of intermediate compound 1 of polymer PBF-STTz1 in Example 1 of the present invention;

[0033] Figure 2 1H NMR spectrum of intermediate compound 3 of polymer PBF-STTz1 in Example 1 of the present invention;

[0034] Figure 3 1H NMR spectrum of intermediate compound 4 of polymer PBF-STTz1 in Example 1 of the present invention;

[0035] Figure 4 1H NMR spectrum of intermediate compound 5 of polymer PBF-STTz1 in Example 1 of the present invention;

[0036] Figure 5 TGA diagrams of polymers PBF-STTz1 and PBSiCl-STTz1 in Experimental Example 1 of the present invention;

[0037] Figure 6 UV-visible absorption spectra of polymers PBF-STTz1 and PBSiCl-STTz1 in Experimental Example 2 of the present invention;

[0038] Figure 7 J–V curves of non-fullerene solar cells prepared from polymers PBF-STTz1 and PBSiCl-STTz1 in Experimental Example 3 of the present invention;

[0039] Figure 8 Cyclic voltammograms of polymers PBF-STTz1 and PBSiCl-STTz1 in Experimental Example 4 of the present invention. Detailed Embodiments

[0040] To make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the drawings and specific embodiments.

[0041] The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention. Without departing from the spirit and essence of the present invention, any modification or replacement made to the methods, steps or conditions of the present invention belongs to the scope of the present invention.

[0042] Example 1

[0043] Synthesis of Polymer PBF-STTz1

[0044] The synthesis route of PBF-STTz1 is as follows:

[0045]

[0046] The specific synthesis steps of PBF-STTz1 are as follows:

[0047] 1. Synthesis of 5-(Bromomethyl)undecane (Compound 1)

[0048]

[0049] Add 2-butylacetate-1-ol (12.5 g, 0.067 mol), triphenylphosphine (26.38 g, 0.101 mol), and 100 mL of dichloromethane into a 250 mL single-necked flask. Then cool it to 0 °C. Slowly add N-bromosuccinimide (16.62 g, 0.094 mol) in batches. After reacting at low temperature for 1 h, stir at room temperature for 4 h. Rotate and evaporate to remove the solvent, and wash the residue with petroleum ether multiple times (a large amount of orange solid does not dissolve). After concentrating the filtrate, the obtained crude product is separated by column chromatography (the eluent is petroleum ether) to obtain colorless oily compound 1 (16.1 g, yield 98%). Compound 1 is directly used in the next step of the reaction.

[0050] The 1H NMR analysis of Compound 1 is as Figure 1 shown: 1 H NMR(400MHz,CDCl3)δ:3.46(t,J=4.0Hz,2H),1.62(m,1H),1.43(m,16H),0.96(m,6H).

[0051] 2. Synthesis of 2-Butyloctane-1-thiol (Compound 2)

[0052]

[0053] Under nitrogen protection, add Compound 1 (12.0 g, 48.2 mmol), thiourea (4.22 g, 55.4 mmol), and 70 mL of absolute ethanol, and stir and react at 80 °C for 24 h. Cool to room temperature, and slowly add 20% sodium hydroxide solution (25 mL) with a syringe, and react at 70 °C for 5 h. After the reaction is completed, cool to room temperature, add an excessive amount of concentrated hydrochloric acid (about 12 - 15 mL) with a syringe, stir for 5 minutes, pour it into water, extract with DCM, and spin dry. Obtain yellow oily compound 2 (7.80 g, yield 80%). Compound 2 is directly used in the next step.

[0054] 3. Synthesis of 4-((2-butyl octyl)thio)thiophene-2-carbaldehyde (Compound 3)

[0055]

[0056] Under nitrogen protection, 2-butyl octane-1-thiol (Compound 2) (7.80 g, 38.56 mmol), 4-bromothiophene-2-carbaldehyde (5.89 g, 30.85 mmol), tetramethylethylenediamine (6.72 g, 57.84 mmol), 120 mg Pd2(dba)3, 150 mg dppf and 150 mL toluene were added to a 250 mL single-necked flask. The mixture was refluxed at 110 °C overnight, and the obtained crude product was separated by column chromatography (eluent: petroleum ether:dichloromethane = 5:1, v / v). Yellow oily liquid Compound 3 (35.0 g, yield 90%) was obtained. Compound 3 was directly used in the next reaction.

[0057] 1H NMR analysis of Compound 3 is as Figure 2 follows: 1 H NMR (400 MHz, CDCl3) δ: 9.88 (s, 1H), 7.68 (s, 1H), 7.49 (s, 1H), 2.89 (t, J = 4.0 Hz, 2H), 1.62 (t, J = 4.0 Hz, 2H), 1.43 (m, 16H), 0.96 (m, 6H).

[0058] 4. Synthesis of 2,5-bis(4-((2-butyl octyl)thio)thiophen-2-yl)thiazolo[5,4-d]thiazole (Compound 4)

[0059]

[0060] Under nitrogen protection, 4-bromothiophene-2-carbaldehyde (15.00 g, 48.05 mmol) and dithiooxamide (1.657 g, 13.73 mmol) were added to 90 mL of anhydrous N,N-dimethylformamide. The mixture was refluxed at 200 °C for 3 days, cooled to room temperature, poured into 50 mL of water, extracted with dichloromethane, and the combined organic phases were dried over anhydrous magnesium sulfate, filtered, and the organic solvents were removed by rotary evaporation under reduced pressure. The obtained crude product was separated by column chromatography (eluent: petroleum ether:dichloromethane = 5:1, v / v), and bright yellow solid Compound 4 (4.79 g, yield: 49.4%) was obtained.

[0061] 1H NMR analysis of Compound 4 is as Figure 3 follows: 11H NMR (400 MHz, CDCl3) δ: 7.47 (s, 2H), 7.19 (s, 2H), 2.90 (s, 4H), 1.61 (s, 2H), 1.43 (m, 32H), 0.92 (m, 12H).

[0062] 5. Synthesis of 2,5-bis(5-bromo-4-((2-butyl octyl)thio)thiophen-2-yl)thiazolo[5,4-d]thiazole (Compound 5)

[0063]

[0064] Under nitrogen protection, compound 4 (4.79 g, 6.78 mmol), 100 mL of chloroform and 40 mL of glacial acetic acid were added to a 250 mL single-necked flask. After complete dissolution, N-bromosuccinimide (3.018 g, 16.96 mmol) was added slowly in portions. Under light protection, the reaction was carried out at room temperature for 12 h. The reaction was stopped, and the reaction solution was transferred to a separatory funnel. 50 mL of distilled water was added, and the mixture was extracted with dichloromethane. The organic phases were combined, dried over anhydrous magnesium sulfate, filtered, and the organic solvents were removed by rotary evaporation under reduced pressure. The obtained crude product was separated by column chromatography (eluent: petroleum ether:dichloromethane = 5:1, v / v), and recrystallized from chloroform and anhydrous methanol to finally obtain bright yellow crystalline compound 5 (1.90 g, yield: 32.5%).

[0065] 1H NMR analysis of compound 5 is as Figure 4 follows: 1 1H NMR (400 MHz, CDCl3) δ: 7.29 (s, 2H), 2.84 - 2.83 (d, J = 4.0 Hz, 4H), 1.55 - 1.52 (s, 2H), 1.40 - 1.19 (s, 32H), 0.85 - 0.78 (m, 12H).

[0066] 6. Synthesis of polymer PBF-STTz1

[0067]

[0068] Under nitrogen protection, compound 5 (159.26 mg, 0.15 mmol), compound 6 (141.08 mg, 0.15 mmol), 20 mg of tetrakis(triphenylphosphine)palladium, and 11 mL of toluene were added to a 25 mL two-necked flask. The reaction was refluxed at 110 °C for 24 h until the reaction system became viscous. Then the mixture was poured into 100 mL of anhydrous methanol and precipitation occurred. After filtration, the polymer was dissolved in chloroform by heating and quickly filtered through a silica gel column (eluent: chloroform). The collected chloroform solution was concentrated and precipitated with anhydrous methanol to obtain a blue-black solid (123 mg). GPC: number average molecular weight (Mn ) = 22.04 kDa; weight-average molecular weight (Mw) = 43.12 kDa, PDI = 1.96.

[0069] Example 2

[0070] Synthesis of polymer PBSiCl-STTz1

[0071] The synthesis route of PBSiCl-STTz1 is as follows:

[0072]

[0073] The specific synthesis steps of PBSiCl-STTz1 are as follows:

[0074] Under nitrogen protection, 2,5-bis(5-bromo-4-((2-butyl octyl)thio)thiophen-2-yl)thiazolo[5,4-d]thiazole (Compound 5, 159.26 mg, 0.15 mmol) prepared in Example 1, Compound 7 (129.75 mg, 0.15 mmol), 20 mg of tetrakis(triphenylphosphine)palladium and 11 mL of toluene were added to a 25 mL two-necked flask, and the mixture was refluxed at 110 °C for 24 h until the reaction system became viscous. Then the mixture was poured into 100 mL of anhydrous methanol for precipitation. After filtration, the polymer was dissolved in chloroform by heating, and the solution was quickly filtered through a silica gel column (eluent: chloroform). The collected chloroform solution was concentrated and precipitated with anhydrous methanol to obtain a blue-black solid (158.8 mg). GPC: number-average molecular weight (M n ) = 23.28 kDa; weight-average molecular weight (Mw) = 62.44 kDa, PDI = 2.68.

[0075] Experimental Example 1

[0076] Thermal stability of the organic polymer donors PBF-STTz1 and PBSiCl-STTz1 prepared in Example 1 and Example 2

[0077] The polymers PBF-STTz1 and PBSiCl-STTz1 prepared in Example 1 and Example 2 were tested for thermal stability using a thermal analyzer (model Perking-El TGA) at a heating rate of 20 °C / min, and the corresponding thermogravimetric curves are as Figure 5 shown. Figure 5 The results show that the thermal decomposition temperatures of the polymers PBF-STTz1 and PBSiCl-STTz1 prepared in Example 1 and Example 2 of the present invention are 377 °C and 355 °C, respectively, indicating that the two polymers have good thermal stability and can be applied to organic solar cells.

[0078] Experimental Example 2

[0079] Photophysical Properties of Organic Polymer Donors PBF-STTz1 and PBSiCl-STTz1 Prepared in Examples 1 and 2

[0080] The ultraviolet-visible (UV-Vis) absorption spectra of the polymers PBF-STTz1 and PBSiCl-STTz1 prepared in Examples 1 and 2 were measured in chloroform solution and in thin film form, respectively. The results are as Figure 6 shown. It Figure 6 can be seen that both polymers PBF-STTz1 and PBSiCl-STTz1 have good light absorption in the range of 300 nm to 650 nm. In the solution state, the maximum absorptions of PBF-STTz1 and PBSiCl-STTz1 are 589 nm and 594 nm, respectively. In the thin film state, the maximum absorptions of the polymers PBF-STTz1 and PBSiCl-STTz1 are 596 nm and 595 nm, respectively, the absorption edges are 672 nm and 670 nm, and the optical band gaps are 1.84 and 1.85 eV, respectively. This indicates that the two polymers are wide band gap polymer materials.

[0081] Experimental Example 3

[0082] Photovoltaic Properties of Organic Polymer Donors PBF-STTz1 and PBSiCl-STTz1 Prepared in Examples 1 and 2

[0083] The current-voltage curves of the bulk heterojunction organic solar cells based on the polymers PBF-STTz1 and PBSiCl-STTz1 are as Figure 7 shown, where when the polymers PBF-STTz1 and PBSiCl-STTz1 are blended with Y6 at a ratio of 1:1.2 respectively, without annealing and additive optimization, the detected photovoltaic performance results are shown in Table 1.

[0084] Table 1 Photovoltaic Performance Results of Polymers PBF-STTz1 and PBSiCl-STTz1

[0085]

[0086] As can be seen from the results in Table 1, when the polymer PBF-STTz1 is blended with Y6, the short-circuit current J sc = 19.21 mA cm -2 , the open-circuit voltage V oc = 0.866 V, the fill factor FF = 62.08%, and the power conversion efficiency PCE = 10.34%; when the polymer PBSiCl-STTz1 is blended with Y6, the short-circuit current J sc = 14.28 mA cm -2 , the open-circuit voltage V oc= 0.882 V, fill factor FF = 61.67%; power conversion efficiency PCE = 6.51%, with good photovoltaic properties.

[0087] Experimental Example 4

[0088] The HOMO and LUMO energy levels of the polymers PBF-STTz1 and PBSiCl-STTz1 prepared in Examples 1 and 2 were measured by cyclic voltammetry (CV). The test conditions were: an acetonitrile solution of 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6), with a Pt working electrode, Ag / AgCl as the reference electrode, and ferrocene (Fc / Fc + ) as the internal standard; the calculation of the electronic energy levels referred to the following empirical formulas: E HOMO = –(E ox on – 0.53) – 4.8 (eV) (1) and E LUMO = E HOMO + E g opt (eV) (2), where E g opt is the optical band gap. The cyclic voltammograms of the two copolymers are as Figure 8 shown. The onset oxidation potentials (E ox on ) of the polymers PBF-STTz1 and PBSiCl-STTz1 are 1.24 V and 1.32 V, respectively. According to E ox on and the empirical formula (1), the HOMO energy levels of the two polymers were calculated to be -5.51 eV and -5.59 eV, respectively. From Figure 8 it can be seen that the onset reduction potential values were not obtained through the test. Therefore, the LUMO energy levels of the polymers were calculated by the empirical formula (2). The calculated results of the LUMO energy levels of PBF-STTz1 and PBSiCl-STTz1 were -3.67 eV and -3.74 eV. The results show that polymers containing C-Cl bonds and σ*(Si)-π*(C) have lower HOMO energy levels, which will be beneficial to increasing the open-circuit voltage value of the device.

[0089] Although the present invention has been described in conjunction with the preferred embodiments, the present invention is not limited to the above embodiments. It should be understood that the appended claims encompass the scope of the present invention. Under the guidance of the inventive concept of the present invention, those skilled in the art should be aware that certain changes made to the embodiments of the present invention will be covered by the spirit and scope of the claims of the present invention.

Claims

1. A dithienylthiazolothiazole polymer substituted with a thioalkane chain, characterized in that, The polymer contains a 2,5-bis(4-((2-butyl octyl)thio)thiophen-2-yl)thiazolo[5,4-d]thiazole structural unit, and its structural formula is shown as Formula I or Formula II below: Wherein n is a positive integer greater than 1.

2. A preparation method of a dithienylthiazolothiazole polymer substituted with a thioalkane chain as described in claim 1, characterized in that, It includes the following steps: reacting compound STTz-Br with 4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)bis(trimethylstannane) and (2,6-bis(trimethylstannanyl)benzo[1,2-b:4,5-b']dithiophene-4,8-diyl)bis(3-chlorothiophene-5,2-diyl))bis(tripropylsilane) respectively through Stille coupling polymerization reaction to obtain; The structure of the compound STTz-Br is shown as Formula III below:

3. The preparation method according to claim 2, characterized in that, The reaction temperature of the Stille coupling polymerization is 110 °C, and the reaction time is 24 h.

4. The preparation method according to claim 2, characterized in that The synthesis method of the compound STTz-Br includes the following steps: S1. Using 2-butyl octan-1-ol as a starting material, reacting with triphenylphosphine and N-bromosuccinimide to obtain a compound a shown as Formula IV; S2. Reacting compound a with thiourea and ethanol in an alkaline environment to obtain a compound b shown as Formula V; S3. Catalytically reacting compound b and 4-bromothiophene-2-carbaldehyde with tetramethylethylenediamine in toluene to obtain a compound c shown as Formula VI; S4. Condensing compound c with dithiooxamide in N,N-dimethylformamide to obtain a compound d shown as Formula VII; S5. Reacting compound d with N-bromosuccinimide in a mixed solution of chloroform and acetic acid to obtain the compound STTz-Br shown as Formula III; 5. The preparation method according to claim 4, characterized in that, In the step S1, the molar ratio of 2-butyl octan-1-ol to N-bromosuccinimide is 1:1 to 2, and the molar ratio of 2-butyl octan-1-ol to triphenylphosphine is 1:1 to 2.

6. The preparation method according to claim 4, characterized in that, In the step S2, the molar ratio of compound a to thiourea is 1:1 to 2, and the solution used in the alkaline environment is NaOH.

7. The preparation method according to claim 4, characterized in that, In the step S3, the catalyst for the catalytic reaction is tris(dibenzylideneacetone)dipalladium and 1,1-bis(diphenylphosphino)ferrocene, and the molar ratio of tris(dibenzylideneacetone)dipalladium to 1,1-bis(diphenylphosphino)ferrocene is 1:2 to 2.

5.

8. The preparation method according to claim 4, characterized in that, In the step S4, the molar ratio of compound c to dithiooxamide is 3 to 3.5:

1.

9. The preparation method according to claim 4, wherein In the step S5, the molar ratio of compound d to N-bromosuccinimide is 1:2 to 2.5, and the volume ratio of chloroform to acetic acid is 2 to 2.5:

1.

10. Application of a thiolane chain-substituted dithienylthiazolothiazole polymer as described in claim 1 or a thiolane chain-substituted dithienylthiazolothiazole polymer prepared by the preparation method according to any one of claims 2 to 9 in the preparation of an organic solar cell.

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