A side chain thiazole-containing benzodithiophene polymer and a preparation method and application thereof

Abstract

The application belongs to the technical field of photoelectric materials, and particularly relates to a side chain thiazole-containing benzo-dithiophene polymer and a preparation method and application thereof. By introducing an electron-deficient thiazole group between a thienyl group on a polymer side chain and a benzo-dithiophene unit on a main chain, one acceptor unit is added to a donor unit of the polymer, a local electron push-pull effect is formed between the thienyl and thiazole on the side chain and between the benzo-dithiophene and thiazole, which is conducive to enhancing the local intramolecular charge transfer, enhancing the intramolecular charge transfer between the donor and acceptor in the whole donor unit, obviously red-shifting the ultraviolet-visible absorption spectrum, red-shifting the strongest absorption peak by 49 nm, enhancing the absorption in the short wave region, and newly appearing a strong absorption peak at 428 nm. The application introduces the electron-deficient thiazole on the side chain, does not contain halogen, is environment-friendly, can widen the light absorption, lower the HOMO energy level, and is conducive to improving the energy conversion efficiency of a photovoltaic device.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic materials technology, specifically relating to a benzodithiophene polymer with thiazole-containing side chains, its preparation method, and its application. Background Technology

[0002] Polymers based on benzodithiophene and benzothiadiazole are DA-type conjugated polymers containing both electron donor (D) and electron acceptor (A) units in their structure, exhibiting excellent photoelectric properties. The active layer in organic solar cells comprises both electron donor and electron acceptor materials; polymers based on benzodithiophene and benzothiadiazole are a type of electron donor material. These polymers can also be used as a material for the light-emitting layer in organic electroluminescent devices and as a material for the organic semiconductor layer in organic field-effect transistors.

[0003] Currently, high-performance donor materials such as PM6 (Adv. Mater. 2015, 27, 4655) and D18 (Sci. Bull. 2020, 65, 272), combined with non-fullerene acceptors such as ITIC (Adv. Mater. 2015, 27, 1170), IT4F (J. Am. Chem. Soc. 2017, 139, 7148), Y6 (Joule 2019, 3, 1140), and PZ1 (Angew. Chem. Int. Ed. 2017, 56, 13503), have achieved high power conversion efficiencies (PCEs). These donor materials are typically based on 4,8-bis(thiophene-2-yl)benzo[1,2- b :4,5- b Dithiophene (BDTT) structural units are widely used due to their excellent charge transport capabilities.

[0004] However, existing technologies still have the following shortcomings: (1) Absorption spectrum mismatch, with weak absorption in the short-wavelength region. Although the acceptor material has strong absorption in the visible-near-infrared region, it cannot be completely complementary to the absorption region of existing donor materials, especially in the short-wavelength region of 350-500 nm. For example, the acceptors ITIC, IT4F, Y6, and PZ1 all have weak absorption in this region. At the same time, the mainstream donor materials PM6 and D18 also have absorption gaps in the 370-460 nm and 300-450 nm, respectively. This lack of absorption spectrum limits the effective utilization of the solar spectrum, especially short-wavelength photons, by the active layer, thus restricting the improvement of short-circuit current density.

[0005] (2) The imperfect energy level structure limits the open-circuit voltage. The highest occupied molecular orbital (HOMO) energy levels of existing donor materials are generally too high, which directly leads to a low open-circuit voltage of the devices. Although this can be improved by constructing ternary or tandem cells, these methods are complex and costly, which is not conducive to practical applications. To reduce the HOMO energy level, the conventional strategy is to introduce halogen atoms such as fluorine (F) or chlorine (Cl). However, the introduction of halogen atoms is often accompanied by complex synthetic routes and increased costs, and halogen-containing materials pose potential hazards to the environment and organisms, which increasingly limits their large-scale application.

[0006] (3) Existing patented technologies are incomplete. Several patented technologies have proposed improvements to address the above problems, but they still fail to completely solve the issues of weak short-wavelength absorption and high HOMO energy levels. Patent CN103848969A discloses a class of polymers containing thiazolyl-dibenzothiophene benzodithiophene, but its core lies in the introduction of new dibenzothiophene-benzodithiophene units, aiming to improve carrier mobility, without specifically addressing the absorption defects in the short-wavelength region. Although patent CN113518780A discloses various benzodithiophene copolymers and their applications in the optoelectronic field, its side-chain or main-chain modification strategies do not focus on simultaneously achieving enhanced short-wavelength absorption and a lower HOMO energy level by introducing electron-deficient groups into the side chains.

[0007] Therefore, how to design and synthesize a novel benzodithiophene polymer donor material that can effectively enhance light absorption in the short-wavelength region (especially 370-450nm) and reduce the HOMO energy level to increase the open-circuit voltage, while avoiding the use of complex halogen-containing synthesis routes, is a technical problem that urgently needs to be solved in the field of organic optoelectronic materials. Summary of the Invention

[0008] The technical problem to be solved by this invention is to provide a benzodithiophene polymer with thiazole-containing side chains, its preparation method and application. By introducing an electron-deficient thiazole group between the thiazole group on the polymer side chain and the benzodithiophene unit on the main chain, an acceptor unit is added to the donor unit of the polymer. A local electron push-pull interaction is formed between the thiazole on the side chain and between the benzodithiophene and the thiazole, which enhances the local intramolecular charge transfer. When applied to electronic devices such as organic solar cells, it is beneficial to increase the short-circuit current density and open-circuit voltage.

[0009] The technical solution adopted is as follows: A benzodithiophene polymer with a thiazole-containing side chain, the polymer having the structural formula shown in formula (I): (I); Among them, R1 and R4 are selected from C4~C 12The alkyl group, R2 and R3 are selected from C1~C3. 10 alkyl groups, n It is an integer between 5 and 1000.

[0010] The benzodithiophene polymer of the present invention contains benzodithiophene, thiophene, and dithienylbenzothiadiazole on its main chain. Furthermore, the side chains of benzodithiophene contain thiazole and thiophene, and an electron-deficient thiazole group is introduced between the thiazole group on the side chain and the benzodithiophene unit on the main chain. In this polymer, the benzodithiophene on the main chain, the thiazole on the side chain, and the thiazole on the main chain are all donor units, while the thiazole on the side chain and the dithienylbenzothiadiazole on the main chain are all acceptor units. This is equivalent to adding an acceptor unit to each side chain of the donor unit, forming a thiazole-acceptor-benzodithiophene linkage structure on the donor unit's side chain. In this linkage structure, a local electron push-pull interaction is formed between the thiazole and benzodithiophene on the side chain, which is beneficial for enhancing local intramolecular charge transfer. A significant red shift occurs in the UV-Vis absorption spectrum, with the strongest absorption peak red-shifted by 49°. The absorption of the nanometer is enhanced in the short-wavelength region, with a new strong absorption peak appearing at 428 nm, which is beneficial to increasing the short-circuit current density. At the same time, the introduction of electron-deficient thiazole units, which are halogen-free, simple to synthesize, low in cost, and environmentally friendly, also lowers the HOMO energy level, which is beneficial to enhancing the open-circuit voltage and thus improving the energy conversion efficiency.

[0011] In the benzodithiophene polymer with thiazole-containing side chains of the present invention, R1 and R2, which are thiophene-linked on the benzodithiophene side chains, and R3 and R4, which are thiophene-linked on the main chain, are all alkyl groups, wherein R1 and R4 are selected from C4~C6. 12 The alkyl group, R2 and R3 are selected from C1~C3. 10 The alkyl group, n is selected from an integer from 5 to 1000, for example: it can be 5, 10, 50, 100, 150, 200, 300, 400, 500, 600, 700, 800, 900 or 1000.

[0012] As a preferred embodiment, in the polymer, n The number of repeating polymer units in this invention can be an integer between 20 and 100, for example: 20, 25, 30, 35, 40, 50, 60, 70, 80, 90 or 100, etc.

[0013] In a preferred embodiment, R1 and R4 in the polymer are -C6H 13R2 and R3 are -C4H9. In the polymers of this invention, the selection of R1, R2, R3, and R4 is determined based on the actual application, and the length of these alkyl chains needs to be considered. If the alkyl chain is too long, it will affect the photoelectric properties of the polymer; if the alkyl chain is too short, the polymer will have poor solubility. The UV-Vis absorption spectra of the polymers of this invention have absorption peaks at 313, 355, 428, 550, and 592 nm, with a new strong absorption peak appearing at 428 nm in the short-wavelength region, indicating a redshift in absorption.

[0014] In a preferred embodiment, the number-average molecular weight of the polymer is 10,000 to 200,000. The number-average molecular weight of the polymer of the present invention can be 10,000, 20,000, 30,000, 40,000, 50,000, 70,000, 80,000, 90,000, 100,000, 150,000, 200,000, etc.

[0015] This invention also provides a method for preparing a benzodithiophene polymer with thiazole-containing side chains, comprising the following steps: S1. Synthesis of Compound A: Tributyl[5-(2-butyloctyl)thiophen-2-yl]stanane and 2-bromothiazole were mixed and an organic solvent was added under an inert gas atmosphere. The mixture was then reacted under heating conditions in the presence of a catalyst. After the reaction was completed, the mixture was cooled, the organic solvent was removed, and the mixture was purified to obtain Compound A. S2. Synthesis of compound B: Under inert gas protection, n-butyllithium was added dropwise to a tetrahydrofuran solution of compound A at low temperature. The mixture was stirred until homogeneous and the reaction was continued at low temperature for 3 h to obtain intermediate a. Benzo[1,2-b:4,5-] was added to the resulting intermediate a under an inert gas atmosphere. b The tetrahydrofuran solution of dithiophene-4,8-dione was stirred until homogeneous and reacted at low temperature for 1 h. The temperature was then slowly raised to room temperature and stirred overnight to obtain intermediate b. Under inert gas protection, a dilute hydrochloric acid solution of tin dichloride was added to the obtained intermediate b, stirred until homogeneous, heated to react overnight, cooled, extracted, concentrated, and purified to obtain compound B. S3. Synthesis of Compound C Under inert gas protection, a hexane solution of n-butyllithium was added dropwise to a tetrahydrofuran solution of the obtained compound B at low temperature. The mixture was stirred and slowly heated to 0 °C for 6 h. Then, a hexane solution of trimethyltin chloride was added dropwise, stirred until homogeneous, and slowly heated to room temperature. The mixture was stirred overnight, quenched, extracted, separated, purified, and dried to obtain compound C. S4. Polymer Synthesis Under inert gas protection, compound D with structural formula (II) was taken, mixed with the obtained compound C, an organic solvent was added and a catalyst was added, and the reaction was stopped after heating for 48 hours or when polymer precipitation occurred. After cooling, precipitation, filtration, and purification, the polymer was obtained; wherein, compound D is 5,8-bis(5-bromo-4-(2-butyloctyl)thiophene)dithieno[3',2':3,4;2'',3'':5,6]benzo[1,2- c [1,2,5]thiadiazole, with the following structural formula: (II).

[0016] Preferably, the inert gas is any one or a mixture of two or more of nitrogen, helium, neon, and argon; The catalyst is any one or both of the following two catalysts: a composite catalyst formed from tris(dibenzylacetone)dipalladium and tris(o-methylphenyl)phosphine, and tetra(triphenylphosphine)palladium. Typically, in the composite catalyst formed from tris(dibenzylacetone)dipalladium and tris(o-methylphenyl)phosphine, the molar ratio of tris(dibenzylacetone)dipalladium to tris(o-methylphenyl)phosphine is 1:5 to 7.

[0017] Preferably, during cooling, all components are cooled to room temperature; The temperature of the low-temperature environment is -80~0 ℃; the overnight stay is 8-12 hours.

[0018] Preferably, in step S1, the molar ratio of tributyl[5-(2-butyloctyl)thiophen-2-yl]stanane to 2-bromothiazole is 1.1~1.3:1, and the amount of catalyst used is 1~5% of the total molar amount of 2-bromothiazole; The reaction was carried out at 90~120 ℃ for 24~48 h with stirring.

[0019] Preferably, in step S2, when preparing intermediate a, the molar ratio of n-butyllithium to compound A is 1.0~1.5:1; In the preparation of intermediate b, compound A reacts with benzo[1,2-b:4,5-] b The molar ratio of dithiophene-4,8-dione is 2~4:1; In the preparation of compound B, tin dichloride reacts with benzo[1,2-b:4,5-] b The molar ratio of dithiophene-4,8-dione is 6~10:1, and the reaction is carried out at 50~70℃.

[0020] Preferably, in step S3, the molar ratio of n-butyllithium to compound B is 2.2~3.0:1; and the molar ratio of trimethyltin chloride to n-butyllithium is 1.0~1.3:1.

[0021] Preferably, in step S4, the molar ratio of compound C to compound D is 1:1; the amount of catalyst used is 0.5-5% of the total molar amount of compound C; and the reaction is carried out at 90-120 °C.

[0022] In steps S1 and S4, the organic solvent is any one or more of tetrahydrofuran, N,N-dimethylformamide, toluene, chlorobenzene, and o-dichlorobenzene; all organic solvents are anhydrous solvents, so that the reactants are dissolved in the solvent for reaction, the ratio of 2-bromothiazole to organic solvent is 0.3~0.5 mol:1 L, and the ratio of compound C to organic solvent is 0.02~0.04 mol:1 L; usually, the organic solvent used is toluene.

[0023] The benzodithiophene polymer with thiazole-containing side chains provided by the present invention or prepared by the method described herein can be used in the fabrication of organic solar cells, organic electroluminescent devices, or organic field-effect transistors.

[0024] The benzodithiophene polymer with a thiazole-containing side chain of the present invention is a DA-type conjugated polymer. Because an electron-deficient thiazole group is introduced between the thiazole group on the side chain and the benzodithiophene unit on the main chain, this polymer exhibits strong local electron push-pull interaction, resulting in a significant red shift in the UV-Vis absorption spectrum. The strongest absorption peak is red-shifted by 49 nm, and absorption in the short-wavelength region is enhanced, with a new strong absorption peak appearing at 428 nm. The introduction of an electron-deficient thiazole on the side chain, the absence of halogens, simple synthesis, low cost, and environmental friendliness, along with the reduction of the HOMO energy level, are beneficial for enhancing... V OC This is beneficial for improving energy conversion efficiency. The benzodithiophene polymer with thiazole-containing side chains of the present invention can be widely used in the fabrication of organic solar cells, organic electroluminescent devices, or organic field-effect transistors. Typically, organic solar cells include an anode, an anode modification layer, an active layer, a cathode modification layer, and a cathode. The active layer includes an electron donor material and an electron acceptor material. In this invention, the electron donor material is the benzodithiophene polymer with thiazole-containing side chains. Organic electroluminescent devices include an anode, a light-emitting layer, a cathode, and a modification layer. In this invention, the light-emitting layer material is the benzodithiophene polymer with thiazole-containing side chains. Organic field-effect transistors include a substrate, an insulating layer, a modification layer, an organic semiconductor layer, a source electrode, and a drain electrode. In this invention, the organic semiconductor layer material is also the benzodithiophene polymer with thiazole-containing side chains.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In this invention, an electron-deficient thiazole group is introduced between the thiophene group on the side chain of the polymer and the benzodithiophene unit on the main chain, thereby adding an acceptor unit to the donor structure of the polymer and forming a connection structure of thiophene on the side chain of the donor unit, thiazole on the acceptor unit, and benzodithiophene on the donor unit. In this connection structure, a local electron push-pull effect is formed between the thiophene and thiazole on the side chain and between benzodithiophene and thiazole, which is beneficial to enhance the local intramolecular charge transfer. This enhances the intramolecular charge transfer between the donor and acceptor in the entire donor unit, and the UV-Vis absorption spectrum shows a significant red shift, with the strongest absorption peak red-shifted by 49 nm. Furthermore, the absorption in the short-wavelength region is enhanced, and a new strong absorption peak appears at 428 nm.

[0026] (2) This invention introduces an electron-deficient thiazole into the side chain, which is halogen-free, simple to synthesize, low in cost, and environmentally friendly. It also lowers the HOMO energy level. The HOMO energy level obtained by cyclic voltammetry is -5.50 eV, a reduction of 0.09 eV, which is beneficial for enhancing the HOMO energy level. V OC This will help improve energy conversion efficiency.

[0027] (3) This invention uses compound D(5,8-bis(5-bromo-4-(2-butyloctyl)thiophene)dithiopheno[3',2':3,4;2'',3'':5,6]benzo[1,2- c [1,2,5]Thiadiazole reacts with compound C to generate a polymer. The bromine in compound D and the tin in compound C are each located at specific carbon sites of the thiophene ring. The Stille coupling reaction can strictly occur at these specific sites. The reaction is well compatible with the complex side chains, thiazolium rings and benzothiadiazole units in compounds D and C, without destroying these key functional structures, resulting in a conjugated polymer with a high molecular weight and a regular main chain. Attached Figure Description

[0028] Figure 1 This is a synthetic route diagram of the polymer PF3 described in this invention.

[0029] Figure 2 The UV-Vis absorption spectrum of the benzodithiophene polymer with thiazole-containing side chains provided by the present invention.

[0030] Figure 3 Cyclic voltammetry curves of the benzodithiophene polymer with thiazole-containing side chains provided by the present invention.

[0031] Figure 4 Open-circuit voltage-short-circuit current density of organic solar cells made from benzodithiophene polymers with thiazole-containing side chains provided in this invention. JV (Line graph) Detailed Implementation

[0032] The accompanying drawings are for illustrative purposes only; to make the technical solution of the present invention clearer, the present invention will be fully described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the described embodiments are only a part of the embodiments of the present invention, and prior art or common general knowledge may be omitted.

[0033] Unless otherwise specified, all reagents or compounds used are conventional products that can be purchased through market sales channels.

[0034] Example 1 A benzodithiophene polymer with thiazole-containing side chains, wherein the number average molecular weight of the polymer in this embodiment is ( M n The value is 21869, and the polydispersity index (PDI) is 3.05.

[0035] like Figure 1 As shown, a method for preparing a benzodithiophene polymer with thiazole-containing side chains according to the present invention includes the following steps: S1. Synthesis of compound A—2-[5-(2-butyloctyl)thiophen-2-yl]thiazole: Under nitrogen protection, 25.61 g (47.29 mmol) of tributyl[5-(2-butyloctyl)thiophen-2-yl]stanane, 8.90 g (54.26 mmol) of 2-bromothiazole, and 2.50 g (2.16 mmol) of tetra(triphenylphosphine)palladium were added to 120 mL of anhydrous toluene as an organic solvent. The mixture was stirred at 110 °C for 38 h, cooled to 25 °C, and toluene was removed by rotary evaporation. The crude product was purified by silica gel column chromatography using petroleum ether and dichloromethane as eluents to obtain compound 1, namely 2-[5-(2-butyloctyl)thiophen-2-yl]thiazole. Compound A is a pale yellow liquid with a mass of 7.76 g and a yield of 48.90%. Its 1H NMR spectrum is as follows: 1 ¹H NMR (600 MHz, CDCl₃) δ 7.72 (d, 1H), 7.34 (d, 1H), 7.19 (d, 1H), 6.72 (d, 1H), 2.76 (d, 2H), 1.63 (m, 1H), 1.29–1.26 (m, 16H), 0.90–0.86 (m, 6H), ¹³C NMR spectrum: 13C NMR (150 MHz, CDCl3) δ 162.47, 147.65, 143.07, 134.81, 126.43, 126.06,117.43, 39.97, 34.63, 33.21, 32.87, 31.90, 29.62, 28.87, 26.62, 22.99, 22.69,14.15,14.12.

[0036] S2. Compound B—4,8-bis(2-(5-(2-butyloctyl)thiophen-2-yl)thiazo-5-yl)benzo[1,2-b:4,5- b Synthesis of dithiophene: Under nitrogen protection, 8.86 mL (22.15 mmol) of n-butyllithium was added dropwise to an anhydrous tetrahydrofuran (40 mL) solution of compound 1 (6.76 g, 20.14 mmol) at -78 °C. The mixture was stirred at -78 °C for 3 h to obtain the reaction solution of intermediate a.

[0037] Under nitrogen protection, benzo[1,2-b:4,5-] was added to the reaction solution of the obtained intermediate a. b A 20 mL solution of anhydrous tetrahydrofuran was prepared of dithiophene-4,8-dione (1.40 g, 6.36 mmol) and stirred at -78 °C for 1 h. The solution was then slowly heated to room temperature and stirred overnight to obtain the reaction solution of intermediate b.

[0038] Under nitrogen protection, a dilute hydrochloric acid solution of tin dichloride (obtained by adding 15.15 g (67.14 mmol) of tin dichloride dihydrate to 34.94 mL of 10% hydrochloric acid) was added to the reaction solution of intermediate b. The mixture was stirred thoroughly and incubated overnight at 60 °C. After the reaction was complete, the temperature was lowered to room temperature, and the solvent was removed by ether extraction to obtain crude compound B. The crude product was purified by silica gel column chromatography using petroleum ether and dichloromethane as eluents to obtain compound B, namely 4,8-bis(2-(5-(2-butyloctyl)thiophene-2-yl)thiazolyl-5-yl)benzo[1,2-b:4,5- b Dithiophene.

[0039] Compound B is a pale yellow solid with a mass of 2.00 g and a yield of 34.75%. Its 1H NMR spectrum is as follows: 1¹H NMR (600 MHz, CDCl₃) δ 8.06 (s, 2H), 7.60 (d, 2H), 7.55 (d, 2H), 7.44 (d, 2H), 6.79 (d, 2H), 2.81 (d, 4H), 1.70 (m, 2H), 1.33–1.26 (m, 32H), 0.92–0.88 (m, 12H), [The remaining text appears to be incomplete and requires further context.] 13 C NMR (150 MHz, CDCl3) δ 163.19, 148.47, 143.24, 139.48,136.95, 134.56, 132.49, 128.51, 127.00, 126.35, 122.83, 120.58, 40.05, 34.75,33.25, 32.91, 31.92,29.65, 28.90, 26.66, 23.02, 22.71, 14.17, 14.14.

[0040] S3. Compound C—5,5'-(2,6-bis(trimethyltinyl)benzo[1,2-b:4,5-] b Synthesis of ']dithiophene-4,8-diyl)bis(2-(5-(2-butyloctyl)thiophene-2-yl)thiazole: Under nitrogen protection, 1.99 mL (3.18 mmol) of a hexane solution of n-butyllithium was slowly added dropwise at -78 °C to a tetrahydrofuran (30 mL) solution of compound B (1.01 g, 1.18 mmol) obtained in step S2. The mixture was stirred and the temperature was slowly raised to 0 °C for 6 h. Then, 4.12 mL of a hexane solution of trimethyltin chloride with a molar concentration of 1.0 mol / L was added dropwise, stirred until homogeneous, and the temperature was slowly raised to room temperature and stirred overnight. The resulting solution was poured into 100 mL of cold water and extracted with diethyl ether to remove the solvent. The crude product was purified by recrystallization from acetone and dried to obtain compound 3, namely 5,5'-(2,6-bis(trimethyltinyl)benzo[1,2-b:4,5-b']dithiophene-4,8-diyl)bis(2-(5-(2-butyloctyl)thiophene-2-yl)thiazole).

[0041] Compound C is a yellow solid with a mass of 0.63 g and a yield of 45.13%. Its 1H NMR spectrum is as follows: 1¹H NMR (600 MHz, CDCl₃) δ 8.06 (s, 2H), 7.62 (t, 2H), 7.46 (d, 2H), 6.79 (d, 2H), 2.82 (d, 4H), 1.70 (m, 2H), 1.33–1.28 (m, 32H), 0.92–0.88 (m, 12H), 0.42 (t, 18H), and the carbon NMR spectrum is as follows: 13 C NMR (150 MHz, CDCl3) δ 162.88, 148.24, 144.04, 143.69,143.19, 137.77, 134.75, 133.29, 130.40, 126.89,126.30, 118.75, 40.06, 34.75,33.24, 32.91, 31.92, 29.66, 28.90, 26.66, 23.03, 22.71, 14.18, 14.14, -8.22.

[0042] S4. Polymer Synthesis Under nitrogen protection, compound D (136.1 mg, 0.15 mmol) of formula (II) and compound C (177.4 mg, 0.15 mmol) obtained in step S3 were added to anhydrous toluene (5 mL) as an organic solvent. Tris(dibenzylacetone)palladium (1.4 mg, 0.0015 mmol) and tris(o-methylphenyl)phosphine (2.8 mg, 0.009 mmol) were added as catalysts. The reaction was carried out at 110 °C for 2 h, and the polymer precipitated. The mixture was then cooled to room temperature. The product was precipitated in methanol, filtered, and the collected crude product was subjected to Soxhlet extraction with methanol and chloroform to remove residual catalyst and oligomers. The undissolved polymer was dissolved in a small amount of o-dichlorobenzene, and the solution was passed through a short silica gel column, concentrated, precipitated in methanol, filtered, and dried in a vacuum drying oven at 37 °C for 24 hours. h, yielding the polymer, namely poly(5-(4,8-bis(2-(5-(2-butyloctyl)thiophene-2-yl)thiazolyl-5-yl)-6-methylbenzo[1,2-b:4,5- b ']dithiophene-2-yl)-4-(2-butyloctyl)thiophene-2-yl)-8-(4-(2-butyloctyl)-5-methylthiophene-2-yl)dithiophene[3',2':3,4;2'',3'':5,6]benzo[1,2- c[1,2,5]thiadiazole, named PF3. Compound D is 5,8-bis(5-bromo-4-(2-butyloctyl)thiophene)dithieno[3',2':3,4;2'',3'':5,6]benzo[1,2- c [1,2,5]thiadiazole.

[0043] The polymer had a mass of 97.0 mg and a yield of 40.30%.

[0044] Test Example 1 The polymer obtained in Example 1 of this invention was prepared into two forms: a chloroform solution and a thin film. The ultraviolet-visible (UV-Vis) absorption spectra were measured in a PerkinElmer Lambda 25 UV-Vis spectrophotometer manufactured by PerkinElmer Inc. The polymer published in the journal Macromolecules (2016, 49, 9358-9370) in 2016 was used as a control sample, named PBDTfDTBT. The experimental results are listed in Table 1.

[0045] Table 1. Results of UV-Vis absorption spectroscopy analysis of different polymers Depend on Figure 2 As shown in Table 1, the benzodithiophene polymer with thiazole-containing side chains of the present invention exhibits good light absorption in the 300-633 nm range. Specifically, in the thin film state, the polymer's absorption peaks are at 310, 350, 420, 540, and 590 nm. Furthermore, there are numerous absorption peaks in the short-wavelength region. Compared to the control sample, the benzodithiophene polymer with thiazole-containing side chains of the present invention shows a new strong absorption peak at 428 nm. This may be due to the local electron push-pull effect formed by the addition of the electron-deficient thiazole unit on the side chain and the formation of the electron-rich thiphene and benzodithiophene units. The strongest absorption peak is at 592 nm, which is 49 nm red-shifted compared to the control sample, covering a wider wavelength range of sunlight. This is because the introduction of thiazole enhances the intermolecular interactions of the polymer. In the solution state, the effect of thiazole on optical properties follows the same pattern. The absorption edge of the benzodithiophene polymer with thiazole-containing side chains of the present invention in the thin film state is 633 nm, which is 7 nm red-shifted compared to the control sample. The optical band gap of the benzodithiophene polymer with thiazole-containing side chains of the present invention ( E g opt The value was 1.96 eV, which was 0.02 eV less than that of the control sample.

[0046] Test Example 2 Cyclic voltammetry curves of the polymer obtained in Example 1 of this invention were measured, and its HOMO and LUMO energy levels were calculated. The polymer named PBDTfDTBT, published in the journal Macromolecules in 2016 (Macromolecules, 2016, 49, 9358-9370) in 2016, was used as a control sample for comparison. The experimental results are listed in Table 2.

[0047] Table 2. Calculation results of energy levels for different polymers Cyclic voltammetry was performed using the standard three-electrode method, with a polymer-coated glassy carbon electrode as the working electrode, a platinum wire as the counter electrode, and a saturated calomel electrode as the reference electrode. The electrolyte was a 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6) anhydrous acetonitrile solution, and the scan rate was 100 mV / s. Ferrocene (Fc / Fc) was used as the reference electrode. + ) is used as an internal standard.

[0048] according to Figure 3 As shown, the oxidation potential of the benzodithiophene polymer with thiazole-containing side chains of the present invention relative to a saturated calomel electrode, measured by cyclic voltammetry, is 1.13 V, and the oxidation potential of ferrocene is 0.4 V; according to the calculation formula... E HOMO = −e( E ox - E (1 / 2，Fc / Fc+) From +4.8), it can be calculated that the HOMO energy level of the benzodithiophene polymer with thiazole-containing side chains of the present invention is -5.53 eV. As shown in Table 2, compared with the control sample, the HOMO energy level of the benzodithiophene polymer with thiazole-containing side chains of the present invention is reduced by 0.09 eV, which is beneficial to improving the performance of photovoltaic devices. V OC ;use E LUMO = E g opt + E HOMO The lowest unoccupied molecular orbital (LUMO) energy level was found to be -3.57 eV.

[0049] Test Example 3 Organic solar cells were fabricated by combining the polymer donor obtained in Example 1 of this invention with a non-fullerene acceptor Y6, and their photovoltaic performance was measured. The device structure was ITO / PEDOT:PSS / PF3:Y6 / PDINO / Al. The ITO substrate was cleaned sequentially with a detergent aqueous solution, a cleaning agent, deionized water, acetone, deionized water, and isopropanol. After drying with a nitrogen gun, the ITO glass substrate was treated with oxygen plasma. The hole transport layer PEDOT:PSS was spin-coated onto the ITO glass at a speed of 4000 rpm for 40 seconds, and then at 150°C. o Annealing at C for 20 min. The active layer solution (PF3:Y6, weight ratio 1:1.2, solid additive thiophene [3,2-]) in chloroform was stirred at room temperature. b Thiophene (TT) and benzo[ b Thiophene (BzT) is 70% of Y6 by weight and has a concentration of 10 mg / mL. -1 After 4 hours, the temperature was increased to 59°C and stirred for 30 minutes, then spin-coated onto a PEDOT:PPS layer and annealed at 100°C for 10 minutes. Finally, the mixture was cooled to below 4 × 10⁻⁶ ℃. -4 Under a pressure of Pa, a metallic electrode Al was evaporated on the electron transport layer. This was achieved under AM 1.5G illumination (100 mW cm⁻¹). -2 Photovoltaic performance was measured. Light intensity was calibrated using a standard silicon solar cell. Test results are shown in Table 3. Figure 4 As shown.

[0050] Table 3 Photovoltaic performance of PF3:Y6-based solar cells As shown in Table 3, the photovoltaic performance test data indicates that when no additives are added to the PF3:Y6 active layer (donor / acceptor ratio of 1:1.2), the open-circuit voltage of the device (…) V OC The voltage is 0.75V, and the short-circuit current density is ( J SC The efficiency of power conversion is 26.71 mA·cm⁻², the fill factor (FF) is 51.20%, and the highest power conversion efficiency (PCE) is [missing information]. max The average power conversion efficiency (PCE) is only 10.32%. ave The overall photovoltaic performance of the device is 10.04%, indicating that its overall photovoltaic performance needs to be improved.

[0051] To optimize device performance, this embodiment introduces TT additive and BzT additive for comparative experiments. Specifically, after introducing the TT additive, the device... V OC Slightly increased to 0.76 V, J SCThe efficiency was increased to 27.19 mA·cm⁻², but the fairing rate (FF) decreased slightly to 51.01%, ultimately resulting in a lower PCE. max It only increased to 10.45% (PCE) ave (The improvement was 10.14%), which was not significant.

[0052] In stark contrast, under the same active layer system and ratio, the photovoltaic performance of the device was significantly improved after the introduction of BzT additive: V OC The voltage was significantly increased to 0.78 V, a 4.0% improvement compared to the additive-free version; the charge transfer efficiency (FF) was substantially increased to 54.37%, a 6.2% improvement compared to the additive-free version, effectively improving the internal charge transport efficiency of the device and reducing charge recombination losses; although J SC It fluctuated slightly down to 26.11 mA·cm⁻², but thanks to... V OC Synergistic gain with FF, device PCE max The efficiency was significantly increased to 11.12%, which is 7.75% higher than that without additives. The average energy conversion efficiency was also increased to 10.57%, and the performance improvement effect was significantly better than that of TT additives.

[0053] In this embodiment, the photovoltaic performance of the device is significantly improved after using solid additives. This is because the molecular structure of the solid additives allows them to form strong intermolecular interactions with the PF3 donor and Y6 acceptor, effectively optimizing the molecular stacking state of the PF3:Y6 active layer, promoting exciton dissociation and charge transport, reducing charge recombination, and thus achieving… V OC The synergistic effect with FF significantly improves the energy conversion efficiency of the device. This technology is simple to implement, cost-effective, and does not require major modifications to existing battery fabrication processes, making it highly practical and promising for industrial application.

[0054] Example 2 A benzodithiophene polymer with thiazole-containing side chains, wherein the number average molecular weight of the polymer in this embodiment is ( M n The value is 35082, and the polydispersity index (PDI) is 3.11.

[0055] Unlike Example 1, R1 is an alkyl group of C4H9 and R2 is an alkyl group of C2H5.

[0056] Other areas not mentioned are the same as in Example 1.

[0057] Example 3 A benzodithiophene polymer with thiazole-containing side chains, wherein the number average molecular weight of the polymer in this embodiment is ( Mn The value is 23926, and the polydispersity index (PDI) is 3.15.

[0058] Unlike Example 1, R4 is an alkyl group of C4H9 and R3 is an alkyl group of C2H5.

[0059] Other areas not mentioned are the same as in Example 1.

[0060] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A benzodithiophene polymer with a thiazole-containing side chain, characterized in that, The structural formula of the polymer is shown in formula (Ⅰ): （Ⅰ）； Among them, R1 and R4 are selected from C4~C 12 The alkyl group, R2 and R3 are selected from C1~C3. 10 alkyl groups, n It is an integer between 5 and 1000.

2. The benzodithiophene polymer with a thiazole-containing side chain according to claim 1, characterized in that, In the polymer, R1 and R4 are -C6H 13 R2 and R3 are -C4H9. n The number is an integer from 20 to 100; the number average molecular weight of the polymer is 10,000 to 200,000.

3. A method for preparing a benzodithiophene polymer with a thiazole-containing side chain as described in claim 1 or 2, characterized in that, Includes the following steps: S1. Synthesis of Compound A: Tributyl[5-(2-butyloctyl)thiophen-2-yl]stanane and 2-bromothiazole were mixed and an organic solvent was added under an inert gas atmosphere. The mixture was then reacted under heating conditions in the presence of a catalyst. After the reaction was completed, the mixture was cooled, the organic solvent was removed, and the mixture was purified to obtain Compound A. S2. Synthesis of compound B: Under inert gas protection, n-butyllithium was added dropwise to a tetrahydrofuran solution of compound A at low temperature. The mixture was stirred until homogeneous and the reaction was continued at low temperature for 3 h to obtain intermediate a. Benzo[1,2-b:4,5-] was added to the resulting intermediate a under an inert gas atmosphere. b The tetrahydrofuran solution of dithiophene-4,8-dione was stirred until homogeneous and reacted at low temperature for 1 h. The temperature was then slowly raised to room temperature and stirred overnight to obtain intermediate b. Under inert gas protection, a dilute hydrochloric acid solution of tin dichloride was added to the obtained intermediate b, stirred until homogeneous, heated to react overnight, cooled, extracted, concentrated, and purified to obtain compound B. S3. Synthesis of Compound C Under inert gas protection, a hexane solution of n-butyllithium was added dropwise to a tetrahydrofuran solution of the obtained compound B at low temperature. The mixture was stirred, heated to 0°C, and reacted for 6 h. Then, a hexane solution of trimethyltin chloride was added dropwise, stirred until homogeneous, heated to room temperature, stirred overnight, quenched, extracted, separated, purified, and dried to obtain compound C. S4. Polymer Synthesis Under inert gas protection, compound D with structural formula (II) was taken, mixed with the obtained compound C, an organic solvent was added and a catalyst was added, and the reaction was stopped after heating for 48 hours or when polymer precipitation occurred. After cooling, precipitation, filtration, and purification, the polymer was obtained; wherein, compound D is 5,8-bis(5-bromo-4-(2-butyloctyl)thiophene)dithieno[3',2':3,4;2'',3'':5,6]benzo[1,2- c [1,2,5]thiadiazole, with the following structural formula: （Ⅱ）。 4. The method for preparing a benzodithiophene polymer with a thiazole-containing side chain according to claim 3, characterized in that, The inert gas is any one or a mixture of two or more of nitrogen, helium, neon, and argon; The catalyst is any one or both of the following two catalysts: a composite catalyst formed from tris(dibenzylideneacetone)dipalladium and tris(o-methylphenyl)phosphine, and tetra(triphenylphosphine)palladium.

5. The method for preparing a benzodithiophene polymer with a thiazole-containing side chain according to claim 3, characterized in that, During cooling, all samples were cooled to room temperature; the temperature of the low-temperature environment was -80~0 ℃; overnight cooling was 8-12 hours.

6. The method for preparing a benzodithiophene polymer with a thiazole-containing side chain according to claim 3, characterized in that, In step S1, the molar ratio of tributyl[5-(2-butyloctyl)thiophen-2-yl]stanane to 2-bromothiazole is 1.1~1.3:1, and the amount of catalyst used is 1~5% of the total molar amount of 2-bromothiazole; the organic solvent is any one or more of tetrahydrofuran, N,N-dimethylformamide, toluene, chlorobenzene, and o-dichlorobenzene. The reaction was carried out at 90~120 ℃ for 24~48 h with stirring.

7. The method for preparing a benzodithiophene polymer with a thiazole-containing side chain according to claim 3, characterized in that, In step S2, when preparing intermediate a, the molar ratio of n-butyllithium to compound A is 1.0~1.5:1; In the preparation of intermediate b, compound A reacts with benzo[1,2-b:4,5-] b The molar ratio of dithiophene-4,8-dione is 2~4:1; In the preparation of compound B, tin dichloride reacts with benzo[1,2-b:4,5-] b The molar ratio of dithiophene-4,8-dione is 6~10:1, and the reaction is carried out at 50~70 °C.

8. The method for preparing a benzodithiophene polymer with a thiazole-containing side chain according to claim 3, characterized in that, In step S3, the molar ratio of n-butyllithium to compound B is 2.2~3.0:1; the molar ratio of trimethyltin chloride to n-butyllithium is 1.0~1.3:

1.

9. The method for preparing a benzodithiophene polymer with a thiazole-containing side chain according to claim 3, characterized in that, In step S4, the molar ratio of compound C to compound D is 1:1; the amount of catalyst used is 0.5-5% of the total molar amount of compound C; the organic solvent is any one or two of tetrahydrofuran, N,N-dimethylformamide, toluene, chlorobenzene, and o-dichlorobenzene; and the reaction is carried out at 90-120 °C.

10. The use of a benzodithiophene polymer with a thiazole-containing side chain prepared by any one of claims 1-2 or 3-9 in the fabrication of organic solar cells, organic electroluminescent devices or organic field-effect transistors.

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