CN104927397A - Poly(triphenylamine-benzothiophene/furan) dye and application thereof - Google Patents

Abstract

The invention discloses a poly(triphenylamine-benzothiophene/furan) dye and its application. The poly(triphenylamine-benzothiophene/furan) dye has a triphenylamine structural unit containing a conjugated system and a carboxyl group and Structural monomer for benzothiophene/furans with long alkyl side chains. The poly(triphenylamine-benzothiophene/furan) dye has good symmetry and solubility, and the rigid planar π-conjugated skeleton can promote electron delocalization and intermolecular interaction, which can effectively improve the charge mobility, and the poly(three Aniline-benzothiophene/furan) dyes can be used as dye layer materials to prepare dye-sensitized solar cells with high current density and high photoelectric conversion efficiency.

Description

Poly(triphenylamine-benzothiophene/furan) dyes and their applications

technical field

The invention relates to a poly(triphenylamine-benzothiophene/furan) dye and its application, and belongs to the field of synthesis and application of functional dyes.

Background technique

With the decrease of petroleum resources and the increase of energy demand, human beings are facing more and more serious energy shortage problems, and people pay more and more attention to the research of low-cost and renewable solar cells. In the field of solar cells, silicon solar cells occupy a relatively large market share due to their high conversion rate and mature technology. However, the raw materials of silicon solar cells are expensive, the production cost is high, and its photoelectric conversion efficiency is difficult to further improve. These defects severely limit development of silicon solar cells. Especially since 1991 by the Swiss Since the dye-sensitized titanium dioxide nano-film new organic solar cell (Nature, 1991, 353, 737) proposed by et al., this type of cell has attracted great attention due to its relatively cheap raw materials, simple preparation process, and high photoelectric conversion efficiency. interest.

After more than 20 years of development, the current dye-sensitized solar cells have approached the photoelectric conversion efficiency of silicon cells. More importantly, the manufacturing cost of dye-sensitized solar cells is only 1/10 of that of silicon cells, which has good application prospects and may replace silicon cells in the future to occupy the solar cell market. At present, dye-sensitized solar cells prepared with organic dye SM315 have achieved a photoelectric conversion efficiency of 13.0% (naturechemistry, 2014, 6, 242). Among them, the use of organic dyes gets rid of the previous high-efficiency dye-sensitized solar cells' dependence on noble metal polypyridine ruthenium dyes, which greatly reduces the cost of the cells. Compared with polypyridine ruthenium complex dyes, the choice of organic dyes is more diverse, its raw materials are abundant, its structure is simple and flexible, its preparation cost is low, its photoelectric conversion efficiency is high, and it has a very high development prospect.

In the research of pure organic small molecule dyes, the photoelectric conversion efficiency is usually improved by broadening the spectral absorption, introducing special groups to inhibit electron recombination, and changing the aggregation state of molecules on the semiconductor surface. At present, the most common system is D-π-A. The light-induced transfer of intramolecular electrons from the D unit to the A unit through the π unit makes photocurrent generation, and the electron transport direction of the molecule is stronger, which greatly improves the conversion efficiency. improve. However, due to the possible desorption of small molecule dyes in the titanium dioxide film and the destabilization of the redox cycle process, its long-term stability needs to be further improved. Therefore, researchers have turned their attention to conjugated polymers as dye sensitizers in DSSCs.

In recent years, there have been many research reports on the application of conductive polymer materials in the fields of organic light-emitting diodes and polymer solar cells. Because conductive polymers combine the structural properties and synthetic advantages of organic polymers with the optoelectronic properties of metals and inorganic semiconductors. Accordingly, many scientific researchers hope to make full use of the advantages of conductive polymer materials to develop polymer dye-sensitized solar cells with high energy conversion efficiency and stability. Because, compared with small molecule dyes, polymer dyes have many potential advantages: on the one hand, a large number of classical structural units can be borrowed from small molecule dyes and polymer solar materials, and their molecular structure design options are more flexible than small molecules. On the other hand, polymers have better light resistance, heat resistance, solvent resistance, and film-forming properties, which can improve the adsorption stability of dyes on _TiO2 films and reduce the desorption of dyes. In addition, by using the barrier effect of the polymer film, it is possible to better inhibit the recombination of the electrons injected into TiO ₂ and the reduced ion I ₃ ^- in the electrolyte.

However, the biggest problem in the development of polymer dyes is their low photoelectric conversion efficiency, which cannot compete with small molecule organic dyes. Among the few existing reports on the application of polymer dyes in DSSCs, the highest photoelectric conversion efficiency is 4.4% (RSC Adv., 2013, 3, 16612-16618). Chinese patent (publication number CN103937292A, published on July 23, 2014) discloses a poly(triphenylamine-phenothiazine) dye and its application in solar cells, which discloses a main chain with phenothiazine And the polymer with triphenylamine structure, the dye-sensitized solar cell with higher current density and high photoelectric conversion efficiency can be prepared by using this polymer. However, its photoelectric conversion efficiency is 2.7-4.7%, which is still difficult to meet the requirements of practical industrial applications. Therefore, for polymer dyes, there is still a lot of room for research.

Contents of the invention

Aiming at the defects of low photoelectric conversion efficiency in the polymer dyes in the prior art, the purpose of the present invention is to improve the structure of the existing poly(triphenylamine-phenothiazine) dyes to obtain a kind of The poly(triphenylamine-benzothiophene/furan) dye of the triphenylamine structural unit of the carboxyl group and the benzothiophene/furan structural unit of the long alkyl chain side chain can be applied to the preparation of relative poly(triphenylamine- Dye-sensitized solar cells with higher photoelectric conversion efficiency and higher current density.

Another object of the present invention is to provide the application of poly(triphenylamine-benzothiophene/furan) dye in the preparation of dye-sensitized solar cells with high current density and high photoelectric conversion rate.

The invention provides a kind of poly(triphenylamine-benzothiophene/furan) dye, poly(triphenylamine-benzothiophene/furan) dye has structural unit shown in formula I:

The molecular weight is 2000-50000;

in,

R is a C ₅ -C ₉ alkoxy group or an alkyl group;

X ₁ and X ₂ are each independently selected from an O atom or an S atom;

π is a group with a conjugated double bond system;

A is a rhodanine-3-acetic acid group, a cyanoacetic acid group or an adipic acid group.

A preferred poly(triphenylamine-benzothiophene/furan) dye R is a C ₅ -C ₉ linear or branched alkoxy group or an alkyl group.

The group having a conjugated double bond system in the preferred poly(triphenylamine-benzothiophene/furan) dye is one of a conjugated olefin group, a conjugated aromatic hydrocarbon group, and a heterocyclic group with a conjugated system or a combination of several.

The group with conjugated double bond system in the preferred poly(triphenylamine-benzothiophene/furan) dye is one or a combination of several.

The group with conjugated double bond system in the further preferred poly(triphenylamine-benzothiophene/furan) dye is one or a combination of several.

Preferred poly(triphenylamine-benzothiophene/furan) dyes A are cyanoacetic acid groups.

The preferred poly(triphenylamine-benzothiophene/furan) dye has a molecular weight of 4,000-30,000.

In the preferred poly(triphenylamine-benzothiophene/furan) dye, π is One or a combination of several of them, A is a cyanoacetic acid group with a molecular weight of 4,000 to 30,000.

Among the groups with a conjugated double bond system, n≥1; R ₂ is a hydrogen atom, halogen, nitro, hydroxyl, amino, cyano, carboxyl, C ₃ -C ₈ alkoxy, C ₃ ~C ₈ alkane group, C ₃ ~C ₈ alkenyl group, C ₅ ~C ₈ acyl group, C ₅ ~C ₇ cycloalkyl group, C ₅ ~C ₁₂ aryl group, five-membered or six-membered hetero One of the ring groups.

In the poly(triphenylamine-benzothiophene/furan) dyestuff of the present invention, the group with the conjugated double bond system mainly serves as the transmission channel for the transfer of electrons from the D unit to the A unit, and along with the extension of the π bond, more Facilitate the flow of electrons and the generation of photocurrent.

The most preferred poly(triphenylamine-benzothiophene/furan) dye has the structure shown in formula II, formula III or formula IV:

The present invention also provides an application of the poly(triphenylamine-benzothiophene/furan) dye, which is to apply the poly(triphenylamine-benzothiophene/furan) dye as a dye layer material to Fabrication of dye-sensitized solar cells.

Poly(triphenylamine-benzothiophene/furan) dye has the structure shown in formula II, formula III or formula IV in the preferred application method:

In the preferred application method, the poly(triphenylamine-benzothiophene/furan) dye is used to prepare a dye layer on the semiconductor nano-titanium dioxide layer, and the semiconductor nano-titanium dioxide layer and the dye layer together form a light-harvesting layer, and the light-harvesting layer is further combined with a transparent The substrate, electrolyte, and counter electrode are assembled into a dye-sensitized solar cell.

In a preferred application method, the poly(triphenylamine-benzothiophene/furan) dye has a structural unit represented by formula II, formula III or formula IV, and has a molecular weight of 4,000-30,000.

The preparation method of poly(triphenylamine-benzothiophene/furan) dye of the present invention is illustrated with the poly(triphenylamine-benzodithiophene) dye with formula II structure as an example:

1. First react 4-bromotriphenylamine with 5-formyl-2-thiopheneboronic acid under the catalysis of ferrocene palladium dichloride to obtain intermediate 2; Free radical substitution reaction to obtain monomer M1;

2. Acylate 3-thiophenecarboxylic acid, oxalyl chloride, and diethylamine in dichloromethane to obtain intermediate 3; the obtained intermediate 3 undergoes a cyclization reaction with n-butyllithium to obtain intermediate 4; the obtained intermediate Reaction of body 4 with sodium hydroxide and isooctane bromide under the catalysis of zinc powder to obtain intermediate 5; obtained intermediate 5 and trimethyltin chloride under conditions of tetrahydrofuran and n-butyllithium to obtain monomer M2; 3. The monomer M1 and the monomer body M2 undergo a Stille coupling reaction under the catalysis of tetrakistriphenylphosphine palladium to obtain the product I; the obtained product I undergoes aldol condensation with cyanoacetic acid to obtain the final product II.

Poly(triphenylamine-phenoxazine) dye synthetic route of the present invention is as follows:

The sensitized solar cell prepared by the poly(triphenylamine-benzothiophene/furan) dye of the present invention and the preparation method of the sensitized solar cell.

The polymer dye-sensitized solar cell of the invention is composed of a transparent substrate (1), a light-harvesting layer (2), an electrolyte layer (3), and a counter electrode (4).

A light-harvesting layer (2) and an electrolyte (3) are sequentially distributed between the transparent substrate (1) and the counter electrode (4).

The transparent base layer (1) is conductive glass (FTO/ITO).

The light-harvesting layer (2) is composed of a semiconductor nano-titanium dioxide layer (5) (the average particle diameter of _TiO2 is not greater than 50nm) and a dye layer (6).

The electrolyte layer (3) is an iodine/lithium iodide electrolyte.

The counter electrode (4) is conductive glass plated with Pt.

The dye layer (6) comprises the poly(triphenylamine-benzothiophene/furan) dye of the present invention.

The preparation method of poly(triphenylamine-benzothiophene/furan) dye-sensitized solar cell of the present invention: on the transparent substrate FTO or ITO, adopt the method for screen printing to coat two layers of nano- _TiO2 films with different particle sizes , the thickness of the bottom layer is 7 μm, the particle size is 20 nm, the particle size of the upper layer is 400 nm, and the thickness is 5 μm; heat-treat the prepared photoanode at 500 ° C for 30 min, and soak it in a solution containing 200 μ g per liter of poly(triphenylamine) after naturally cooling to 80 ° C -Benzothiophene/furan) and acetonitrile/tetrahydrofuran (1:1), sensitize for 12 to 24 hours; after sensitization, wash with acetonitrile and dry for use; plate Pt on the pretreated FTO conductive glass substrate to make Counter electrode; place the sensitized photoanode upwards on the hot press, cover the TiO ₂ film with a 30 μm thick Surlyn ring, cover the counter electrode, and then heat seal at 100 ° C for 2 minutes; drop on the small hole of the counter electrode 1 drop of electrolyte, after using a diaphragm pump to evacuate the air bubbles between the two electrodes, seal it to prepare a dye-sensitized solar cell.

Beneficial effects of the present invention: the present invention improves the structure of existing poly(triphenylamine-phenothiazine) dye polymers, and adopts benzothiophene/or furan structural units with long alkyl chains to replace poly(triphenylamine-phenothiazine) Phenothiazine structural units in dye polymers, unexpected discovery of benzothiophene and/or furan structural units with long alkyl chains and triphenylamine structural units with thiophene and cyanoacetic acid electron-withdrawing side chains In combination, relative to the poly(triphenylamine-phenothiazine) dye, the charge mobility can be significantly improved, and a dye-sensitized solar cell with higher photoelectric conversion efficiency can be obtained. In the poly(triphenylamine-benzothiophene/furan) dye of the present invention, the triphenylamine structure and two or more donor units of conjugated structures with different electron-donating properties are organically compounded by copolymerization, effectively improving the transfer efficiency of electrons in the molecule ; and more long-chain alkyl groups are grafted on the main chain to enhance the flexibility of molecules and reduce the aggregation of dyes, improve the photovoltage of the device, and make the dyes have better light absorption ability. At the same time, the side chain grafted thiophene and other structures are bridging units and cyanoacetic acid electron-absorbing units, which effectively increase the solubility and electronic properties of the polymer material, and obtain a high current density and high photoelectric conversion rate. Triphenylamine-based polymer dyes for dye-sensitized solar cells.

Description of drawings

[Fig. 1] is a schematic structural view of a polymer dye-sensitized solar cell based on the present invention; 1 is a transparent substrate, 2 is a light-harvesting layer, 3 is an electrolyte layer, 4 is a counter electrode, 5 is a semiconductor nano-titanium dioxide layer, and 6 is Dye layer.

[ Fig. 2 ] is a graph of photoelectric conversion efficiency and wavelength of the dye-sensitized solar cells prepared in Examples 1-3 of the present invention.

[ Fig. 3 ] is a graph showing the relationship between current and voltage of the dye-sensitized solar cell prepared in the embodiment of the present invention.

Detailed ways

The following examples are intended to further illustrate the content of the present invention, rather than limit the protection scope of the claims of the present invention.

Example 1

Synthesis of polymer dye sensitizer with structural unit of formula II and application in dye-sensitized solar cells.

The synthetic route is as follows:

Synthesis of intermediate (2):

Add 12.96g of 4-bromotriphenylamine, 12.4g of 5-formyl-2-thiophene boronic acid, and 27.6g of anhydrous potassium carbonate into the reaction flask, then add 100mL of toluene, 100mL of methanol, and add the catalyst ferrocene di palladium chloride. Heated to 70°C and followed the reaction to completion. The reaction was quenched by adding 150 mL of water and extracted with dichloromethane. The organic layers were combined, dried over anhydrous sodium sulfate, and filtered. The crude product was separated and purified by column chromatography (silica gel column, eluent: n-hexane/dichloromethane=4/1) to obtain pure intermediate 2 as a yellow solid with a yield of 60.2%.

NMR characterization data of intermediate (2):

¹ H NMR(CDCl ₃ ,400MHz,ppm):δ=9.91(s,1H),7.72(d,1H),7.54(d,2H),7.36(m,5H),7.18(d,4H),7.14 -7.13(m,4H).

Synthesis of intermediate monomer (M1):

3.56g of intermediate 2 was dissolved in 100mL of anhydrous tetrahydrofuran and cooled to 0°C. Add 3.56g of N-bromosuccinimide at one time in the dark, and stir at 0°C for 2h. Rise to room temperature to continue the reaction, follow the reaction until the reaction is complete. The reaction was quenched with water, extracted with ethyl acetate, and dried over anhydrous magnesium sulfate. After filtration, the crude product was separated and purified by column chromatography (silica gel column, petroleum ether/dichloromethane=4/1-2/1, v/v) to obtain intermediate M1 as a yellow powder with a yield of 90.1%.

NMR characterization data of intermediate monomer (M1):

¹ H NMR(CDCl ₃ ,400MHz,ppm):δ=9.81(s,1H),7.75(d,1H),7.57-7.55(d,2H),7.43(d,4H),7.35(d,1H) ,7.08(m,2H),7.03(m,4H).

Synthesis of intermediate (3):

Add 12.8g of 3-thiophenecarboxylic acid and 30mL of dichloromethane into a 250mL three-necked flask. Add 25.4 g of oxalyl chloride at one time under the condition of ice-water bath, stir overnight at room temperature, and spin the obtained liquid to dry the solvent to obtain a colorless solid, which is dissolved in 50 mL of dichloromethane. Dissolve 14.6 g of diethylamine in 50 mL of dichloromethane, place in an ice-water bath, and slowly drop the liquid obtained in the previous step into the diethylamine mixed solution. After the dropwise addition was completed, stir at room temperature for 1 h. After the reaction was completed, cool to room temperature, extract with dichloromethane, wash with water several times, remove the solvent by rotary evaporation, and separate the crude product by column chromatography (neutral alumina column, eluting with petroleum ether). Intermediate 3 was obtained as light yellow oily liquid with a yield of 85%.

NMR characterization data of intermediate (3):

¹ H NMR (CDCl ₃ , 400 MHz): 7.46 (s, 1H), 7.30 (d, 1H), 7.28 (d, 1H), 3.49 (m, 4H), 1.25 (t, 6H).

Synthesis of intermediate (4):

Add 3.66g of intermediate 3 into a closed three-necked flask, inject 80mL of anhydrous tetrahydrofuran under nitrogen protection, and cool to -78°C. After stirring for 20 min, 8.3 mL of n-butyllithium was added to the reaction system using a constant pressure dropping funnel. The reaction system was stirred at room temperature for 30 min, then the reactant was poured into 200 mL of ice water, stirred overnight, and the mixture was filtered to obtain 3.01 g of a yellow solid with a yield of 70%.

NMR characterization data of intermediate (4):

¹ H NMR (CDCl ₃ , 400 MHz, ppm): 7.82 (d, 2H), 8.01 (d, 2H).

Synthesis of intermediate (5):

Add 2.2g of intermediate 3, 1.43g of zinc powder and 40mL of water into a 250mL three-necked flask, and then add 6g of sodium hydroxide into the mixed system. The mixed system was heated and stirred for 1 h, and then 5.8 g of isooctane bromide and a small amount of tetrabutylsodium bromide were added to the mixed system. After the reaction system was stirred for 2 hours, 0.65 g of zinc powder was added and reacted overnight. After the reaction was finished, it was washed with water and extracted with ethyl acetate, dried over anhydrous MgSO ₄ , and the crude product was recrystallized from ethanol to obtain intermediate 5 as white crystals with a yield of 68%.

NMR characterization data of intermediate (5):

¹ H NMR (CDCl ₃ , 400 MHz, ppm): 7.51 (d, 2H), 6.90 (d, 2H), 3.13 (m, 2H), 1.21-1.56 (m, 32H).

Synthesis of intermediate monomer (M2):

2.67g of intermediate 5 was added into a dry three-necked flask, the gas was pumped out three times, and 80mL of THF was injected under the protection of nitrogen. Move the reaction system to a low-temperature reaction kettle, lower it to -78°C, and add 8.73mL of n-butyllithium dropwise with a constant pressure dropping funnel, first lithiate at -78°C for 1h, and then transfer to room temperature for 1h. Then inject 24 mL of trimethyltin chloride at -78°C and react overnight. After the reaction is complete, cool down to room temperature, spin dry the solvent, wash with water, extract with dichloromethane, and dry over anhydrous sodium sulfate. After filtration, the solvent was removed by rotary evaporation, and the crude product was recrystallized from isopropanol to obtain the pure intermediate monomer M2 as a light brown solid with a yield of 50%.

NMR characterization data of intermediate monomer (M2):

¹ H NMR (CDCl ₃ , 400 MHz): 7.28 (s, 2H), 2.65 (m, 2H), 1.82-1.59 (m, 20H), 0.54 (t, 30H).

Synthesis of polymer intermediate (i):

Add 0.26g of intermediate M1 and 0.55g of intermediate M2, 25mL of toluene into a 50mL three-necked flask, and add 0.04g of tetrakistriphenylphosphine palladium catalyst under nitrogen protection. The mixed reactant was inflated and deflated three times, heated up to 110° C. and reacted with vigorous stirring for 48 hours. After the reaction is complete, pour into 150mL methanol, filter, and collect the precipitate. The crude product was Soxhlet extracted with methanol and n-hexane for 24h to remove the monomer. Finally, Soxhlet extraction with chloroform was used for 24 hours to fully dissolve the polymer. The solvent was removed by rotary evaporation, and vacuum-dried for 24 h to obtain polymer intermediate i as a dark brown film-like solid with a yield of 60.5%.

NMR characterization data of polymer intermediate (i):

¹ H NMR (CDCl ₃ , 400 MHz, ppm): 9.88 (s, 1H), 7.03-6.90 (d, 16H), 1.40-1.18 (m, 22H), 0.88-0.81 (m, 12H).

Synthesis of polymer dyes with structural units of formula II:

0.47g of polymer intermediate i, 0.145g of cyanoacetic acid, and 20mL of chloroform were added to the reaction flask. Under nitrogen protection, stir to dissolve. Inject 0.4 mL of piperidine using a syringe, heat up to reflux, and react for 10 h. After the reaction was complete, it was cooled to room temperature, and washed successively with 2M hydrochloric acid solution and saturated brine. Dry over anhydrous magnesium sulfate. After filtration, the solvent was removed by rotary evaporation, and the polymer dye with the structure of formula (II) was obtained after further purification as a dark red film-like solid with a yield of 75.7%.

The nuclear magnetic characterization data of the polymer with formula II structural unit:

¹ H NMR(DMSO,400MHz,ppm):13.15(s,1H),8.86(s,1H),7.51-6.92(d,16H),1.66-1.34(m,22H),0.65-0.61(m,12H ).

Example 2

Synthesis of polymer dye sensitizer with structural unit of formula III and application in dye-sensitized solar cells.

The synthetic route is as follows:

Synthesis of intermediate (2):

Add 12.96g of 4-bromotriphenylamine, 12.4g of 5-formyl-2-thiophene boronic acid, and 27.6g of anhydrous potassium carbonate into the reaction flask, then add 100mL of toluene, 100mL of methanol, and add the catalyst ferrocene di palladium chloride. Heated to 70°C and followed the reaction to completion. The reaction was quenched by adding 150 mL of water and extracted with dichloromethane. The organic layers were combined, dried over anhydrous sodium sulfate, and filtered. The crude product was separated and purified by column chromatography (silica gel column, eluent: n-hexane/dichloromethane=4/1) to obtain pure intermediate 2 as a yellow solid with a yield of 60.2%.

NMR characterization data of intermediate (2):

¹ H NMR(CDCl ₃ ,400MHz,ppm):δ=9.91(s,1H),7.72(d,1H),7.54(d,2H),7.36(m,5H),7.18(d,4H),7.14 -7.13(m,4H).

Synthesis of intermediate monomer (M1):

3.56g of intermediate 2 was dissolved in 100mL of anhydrous tetrahydrofuran and cooled to 0°C. Add 3.56g of N-bromosuccinimide at one time in the dark, and stir at 0°C for 2h. Rise to room temperature to continue the reaction, follow the reaction until the reaction is complete. The reaction was quenched with water, extracted with ethyl acetate, and dried over anhydrous magnesium sulfate. After filtration, the crude product was separated and purified by column chromatography (silica gel column, petroleum ether/dichloromethane=4/1-2/1, v/v) to obtain intermediate M1 as a yellow powder with a yield of 90.1%.

NMR characterization data of intermediate monomer (M1):

¹ H NMR(CDCl ₃ ,400MHz,ppm):δ=9.81(s,1H),7.75(d,1H),7.57-7.55(d,2H),7.43(d,4H),7.35(d,1H) ,7.08(m,2H),7.03(m,4H).

Synthesis of intermediate (6):

Add 25.1g of 3-furancarboxylic acid into 65.3mL of thionyl chloride, reflux at 78°C for 4h to stop the reaction, and spin off excess thionyl chloride. Then the reactant was added dropwise to the mixed system of diethylamine (92.6 mL) and dichloromethane (100 mL), and the dropwise addition was completed at 0°C. After dropping, react at room temperature for 1 h. Then the mixture was poured into ice water, extracted with dichloromethane, washed with water, and the organic phase was spin-dried, and the crude product was passed through the column with petroleum ether. Intermediate 6 was obtained as light yellow oily liquid with a yield of 84%.

NMR characterization data of intermediate (6):

¹ H NMR (CDCl ₃ , 400 MHz): 7.76 (s, 1H), 7.30 (d, 1H), 7.28 (d, 1H), 3.49 (m, 4H), 1.25 (t, 6H).

Synthesis of intermediate (7):

Add 8.36g of intermediate 6 into a closed three-necked flask, inject 200mL of anhydrous tetrahydrofuran under nitrogen protection, and cool to -78°C. After stirring for 20 min, 22 mL of n-butyllithium was added to the reaction system using a constant pressure dropping funnel. The reaction system was stirred at room temperature for 30 min. Then, 4.7 mL of 3-thiophenecarboxylic acid in THF was slowly added dropwise to the system. After the system was stirred for 2 hours, 22 mL of n-butyllithium was added to the system, raised to room temperature, and reacted overnight. After the reaction was completed, the solvent was spin-dried, and the system was cooled to 4° C., and filtered to obtain a solid. The filtrate was extracted with dichloromethane, and the organic phase was spin-dried. The organic phases were combined and purified by column chromatography to obtain a yellow solid with a yield of 46%.

NMR characterization data of intermediate (7):

¹ H NMR (CDCl ₃ , 400 MHz, ppm): 8.05 (d, 1H), 7.69 (d, 1H), 7.36 (d, 1H), 6.57 (d, 1H).

Synthesis of intermediate (8):

Add 2.4g of intermediate 7, 1.43g of zinc powder and 33mL of distilled water into a 250mL three-necked flask, and then add 6g of sodium hydroxide into the mixed system. The mixed system was heated to 100° C. and stirred and refluxed for 1 h, and then 5.8 g of bromoisoctane and 1.33 g of tetrabutylsodium bromide were added to the mixed system. The reaction system continued to reflux for 2h. Then add 0.65g of zinc powder and react overnight. After the reaction, the reactant was poured into ice water, extracted with dichloromethane, dried over anhydrous MgSO ₄ , and the crude product was recrystallized from ethanol to obtain intermediate 8 as a white oily liquid with a yield of 60%.

NMR characterization data of intermediate (8):

¹ H NMR(CDCl ₃ ,400MHz,ppm):7.86(d,1H),7.82(d,1H),7.65(d,1H),7.44(d,1H),4.87(m,2H),1.76-1.35 (m,20H), 1.21-0.99(t,12H).

Synthesis of intermediate monomer (M3):

0.86g of intermediate 8 was added to a dry three-necked flask, the gas was pumped out three times, and 50mL of THF was injected under the protection of nitrogen. Move the reaction system to a low-temperature reaction kettle, lower it to -78°C, and add 2.91mL of n-butyllithium dropwise with a constant pressure dropping funnel, first lithiate at -78°C for 1h, and then transfer to room temperature for 1h. Then inject 8 mL of trimethyltin chloride at -78°C and react overnight. After the reaction is complete, cool down to room temperature, spin dry the solvent, wash with water, extract with dichloromethane, and dry over anhydrous sodium sulfate. After filtration, the solvent was removed by rotary evaporation, and the crude product was recrystallized from isopropanol to obtain the pure intermediate monomer M3 as a pale yellow solid with a yield of 81%.

NMR characterization data of intermediate monomer (M3):

¹ H NMR (CDCl ₃ , 400 MHz): 7.67 (s, 1H), 7.21 (s, 1H), 3.34 (m, 2H), 1.95-1.67 (m, 20H), 0.66-0.53 (t, 30H).

Synthesis of polymer intermediate (ii):

Add 0.26g of intermediate M1 and 0.54g of intermediate M3, 25mL of toluene into a 50mL three-necked flask, and add 0.03g of tetrakistriphenylphosphine palladium catalyst under nitrogen protection. Inflate and deflate again three times, heat up to 110°C and react with vigorous stirring for 48h. After the reaction is complete, pour into 150mL methanol, filter, and collect the precipitate. The crude product was Soxhlet extracted with methanol and n-hexane for 24h to remove the monomer. Finally, Soxhlet extraction with chloroform was used for 24 hours to fully dissolve the polymer. The solvent was removed by rotary evaporation, and vacuum-dried for 24 h to obtain polymer intermediate ii as a bright black film-like solid with a yield of 83%.

The NMR characterization data of polymer intermediate (ii):

¹ H NMR(CDCl ₃ ,400MHz,ppm): ¹ H NMR(CDCl ₃ ,400MHz):9.57(s,1H),7.56(s,1H),7.48(s,1H),7.03-6.96(d,14H ), 1.49-1.25(m,22H), 0.86-0.77(m,12H).

Synthesis of polymeric dyes with structural units of formula III:

0.46g of polymer intermediate (ii), 0.15g of cyanoacetic acid, and 20mL of chloroform were added to the reaction flask. Under nitrogen protection, stir to dissolve. Inject 0.39 mL of piperidine using a syringe, raise the temperature to 75°C and reflux, and react for 10 h. After the reaction was complete, it was cooled to room temperature, and washed successively with 2M hydrochloric acid solution and saturated brine. The organic phases were combined and dried over anhydrous magnesium sulfate. After filtration and rotary evaporation to remove the solvent, polymer dye III was obtained after further purification as a dark brown solid with a yield of 85%.

The nuclear magnetic characterization data of the polymer with formula III structural unit:

¹ H NMR(DMSO,400MHz,ppm):13.69(s,1H),8.09(s,1H),7.79(s,1H),7.73(s,1H),7.55-6.62(d,14H),1.87- 1.54(m,22H),0.65-0.43(m,12H).

Example 3

Synthesis of polymer dye sensitizer with structural unit of formula IV and application in dye-sensitized solar cells.

The synthetic route is as follows:

Synthesis of intermediate (2):

Add 12.96g of 4-bromotriphenylamine, 12.4g of 5-formyl-2-thiophene boronic acid, and 27.6g of anhydrous potassium carbonate into the reaction flask, then add 100mL of toluene, 100mL of methanol, and add the catalyst ferrocene di palladium chloride. Heated to 70°C and followed the reaction to completion. The reaction was quenched by adding 150 mL of water and extracted with dichloromethane. The organic layers were combined, dried over anhydrous sodium sulfate, and filtered. The crude product was separated and purified by column chromatography (silica gel column, eluent: n-hexane/dichloromethane=4/1) to obtain pure intermediate 2 as a yellow solid with a yield of 60.2%.

NMR characterization data of intermediate (2):

¹ H NMR(CDCl ₃ ,400MHz,ppm):δ=9.91(s,1H),7.72(d,1H),7.54(d,2H),7.36(m,5H),7.18(d,4H),7.14 -7.13(m,4H).

Synthesis of intermediate monomer (M1):

3.56g of intermediate 2 was dissolved in 100mL of anhydrous tetrahydrofuran and cooled to 0°C. Add 3.56g of N-bromosuccinimide at one time in the dark, and stir at 0°C for 2h. Rise to room temperature to continue the reaction, follow the reaction until the reaction is complete. The reaction was quenched with water, extracted with ethyl acetate, and dried over anhydrous magnesium sulfate. After filtration, the crude product was separated and purified by column chromatography (silica gel column, petroleum ether/dichloromethane=4/1-2/1, v/v) to obtain intermediate M1 as a yellow powder with a yield of 90.1%.

NMR characterization data of intermediate monomer (M1):

¹ H NMR(CDCl ₃ ,400MHz,ppm):δ=9.81(s,1H),7.75(d,1H),7.57-7.55(d,2H),7.43(d,4H),7.35(d,1H) ,7.08(m,2H),7.03(m,4H).

Synthesis of intermediate (6):

Add 25.1g of 3-furancarboxylic acid into 65.3mL of thionyl chloride, reflux at 78°C for 4h to stop the reaction, and spin off excess thionyl chloride. Then the reactant was added dropwise to the mixed system of diethylamine (92.6 mL) and dichloromethane (100 mL), and the dropwise addition was completed at 0°C. After dropping, react at room temperature for 1 h. Then the mixture was poured into ice water, extracted with dichloromethane, washed with water, and the organic phase was spin-dried, and the crude product was passed through the column with petroleum ether. Intermediate 6 was obtained as light yellow oily liquid with a yield of 84%.

NMR characterization data of intermediate (6):

¹ H NMR (CDCl ₃ , 400 MHz): 7.76 (s, 1H), 7.30 (d, 1H), 7.28 (d, 1H), 3.49 (m, 4H), 1.25 (t, 6H).

Synthesis of intermediate (9):

Add 8.35g of intermediate 6 into a three-neck flask, pump out the gas to make the inside of the bottle an inert environment, pour into 50mL of anhydrous tetrahydrofuran, cool to 0°C, and stir for 30min. Add 21 mL of n-butyllithium dropwise with a constant pressure dropping funnel, and finish dropping in 30 minutes. After completion, stir at 0°C for 30 minutes, then raise the temperature to 66°C and reflux for 4 hours. After the reaction was completed, it was cooled to room temperature, the reaction system was poured into ice water, and stirred for several hours to obtain pure intermediate 8 as a yellow solid with a yield of 65%.

NMR characterization data of intermediate (9):

¹ H NMR (CDCl ₃ , 400 MHz, ppm): 8.70 (d, 1H), 8.12 (d, 1H), 7.86 (d, 1H), 7.57 (d, 1H).

Synthesis of intermediate (10):

Add 1.88g of intermediate 9, 1.43g of zinc powder and 33mL of distilled water into a 250mL three-necked flask, and then add 6g of sodium hydroxide into the mixed system. The mixed system was heated to 100° C. and stirred and refluxed for 1 h, and then 5.8 g of bromoisoctane and 1.33 g of tetrabutylsodium bromide were added to the mixed system. The reaction system continued to reflux for 2h. Then add 0.65g of zinc powder and react overnight. After the reaction was completed, the reactant was poured into ice water and extracted with dichloromethane, dried over anhydrous _MgSO4 , and the crude product was recrystallized from ethanol to obtain intermediate 10 as white crystals with a yield of 51%.

NMR characterization data of intermediate (10):

¹ H NMR (CDCl ₃ , 400 MHz, ppm): 7.71-7.20 (d, 4H), 5.03 (m, 2H), 1.96-1.29 (m, 20H), 1.33-0.83 (t, 12H).

Synthesis of intermediate monomer (M4):

0.83g of intermediate 8 was added into a dry three-necked flask, the gas was pumped out three times, and 50mL of THF was injected under the protection of nitrogen. Move the reaction system to a low-temperature reaction kettle, lower it to -78°C, and add 2.91mL of n-butyllithium dropwise with a constant pressure dropping funnel, first lithiate at -78°C for 1h, and then transfer to room temperature for 1h. Then inject 8 mL of trimethyltin chloride at -78°C and react overnight. After the reaction is complete, cool down to room temperature, spin dry the solvent, wash with water, extract with dichloromethane, and dry over anhydrous sodium sulfate. After filtration, the solvent was removed by rotary evaporation, and the crude product was recrystallized from isopropanol to obtain the pure intermediate monomer M3 as a light yellow solid with a yield of 76%.

NMR characterization data of intermediate monomer (M4):

¹ H NMR (CDCl ₃ , 400 MHz): 6.67 (s, 2H), 3.94 (m, 2H), 1.90-1.73 (m, 20H), 0.62-0.59 (t, 30H).

Synthesis of polymer intermediate (iii):

Add 0.26 g of intermediate M1 and 0.54 g of intermediate M4, 25 mL of toluene into a 50 mL three-necked flask, and add 0.05 g of tetrakistriphenylphosphine palladium catalyst under nitrogen protection. The mixed reactant was inflated and deflated three times, heated up to 110° C. and reacted with vigorous stirring for 48 hours. After the reaction is complete, pour into 150mL methanol, filter, and collect the precipitate. The crude product was Soxhlet extracted with methanol and n-hexane for 24h to remove the monomer. Finally, Soxhlet extraction with chloroform was used for 24 hours to fully dissolve the polymer. The solvent was removed by rotary evaporation, and vacuum-dried for 24 hours to obtain polymer intermediate i as a dark brown film-like solid with a yield of 73.3%.

NMR characterization data of polymer intermediate (i):

¹ H NMR (CDCl ₃ , 400 MHz, ppm): 9.54 (s, 1H), 7.78-6.81 (d, 16H), 1.72-1.31 (m, 22H), 0.90-0.88 (m, 12H).

Synthesis of polymer dyes with structural units of formula IV:

0.463g of polymer intermediate iii, 0.145g of cyanoacetic acid, and 20mL of chloroform were added to the reaction flask. Under nitrogen protection, stir to dissolve. Inject 0.4 mL of piperidine using a syringe, heat up to reflux, and react for 10 h. After the reaction was complete, it was cooled to room temperature, and washed successively with 2M hydrochloric acid solution and saturated brine. Dry over anhydrous magnesium sulfate. After filtration, the solvent was removed by rotary evaporation, and the polymer dye with the structure of formula (II) was obtained after further purification as a dark brown solid with a yield of 82%.

The nuclear magnetic characterization data of the polymer with formula II structural unit:

¹ H NMR(DMSO,400MHz,ppm):12.76(s,1H),8.26(s,1H),7.76-6.92(d,16H),1.61-1.29(m,22H),0.87-0.74(m,12H ).

Example 4

The transparent substrate of the dye-sensitized solar cell is purchased FTO or ITO, and then two layers of nano- _TiO2 films with different particle sizes are coated on the transparent substrate by screen printing. The thickness of the bottom layer is 7 μm and the particle size is 20 nm. The particle diameter of the upper layer is 400 nm, and the thickness is 5 μm. Heat-treat the prepared photoanode at 500°C for 30 minutes, and then soak it in a solution containing 200 μg per liter of polymer dye and acetonitrile/tetrahydrofuran (1:1) after naturally cooling to 80°C, and sensitize for 12 to 24 hours; after sensitization, use acetonitrile Wash and dry for use; the polymer dye is the polymer dye prepared in Example 1, Example 2 or Example 3.

Plating Pt on the pretreated FTO conductive glass substrate is done as counter electrode; Place the good photoanode of sensitization upwards on the hot press, and surround the _TiO film with a 30 μm thick Surlyn ring (7 in the accompanying drawing 1), Cover the counter electrode, and then heat seal it at 100°C for 2 minutes; drop 1 drop of electrolyte on the small hole of the counter electrode, use a diaphragm pump to vacuumize the gap between the two electrodes, and then seal it to obtain a dye-sensitized solar energy Battery; the performance results of the dye-sensitized solar cell are shown in Table 1.

Table 1 Performance results of dye-sensitized solar cells

From the data in Table 1, it can be seen that the solar cell obtained by a series of poly(triphenylamine-benzothiophene/furan) dyes prepared by the present invention has overall higher photoelectric conversion efficiency (5.21～6.41%), compared with poly(triphenylamine-benzothiophene/furan) The photoelectric conversion efficiency (2.7～4.7%) of solar cells prepared by aniline-phenothiazine) dyes has a qualitative leap, calculated by the average photoelectric conversion efficiency of solar cells prepared by two series of polymer dyes, the photoelectric conversion efficiency of solar cells of the present invention The conversion efficiency increased by about 56%.

Claims (10)

1. A poly (triphenylamine-benzothiophene/furan) dye characterized by having a structural unit represented by formula I:

the molecular weight is 2000-50000;

wherein,

r is C₅～C₉Alkoxy or alkyl of, X₁And X₂Each independently selected from an O atom orAn S atom;

pi is a group having a conjugated double bond system;

a is a rhodanine-3-acetic acid group, a cyanoacetic acid group or an adipic acid group.

2. The poly (triphenylamine-benzothiophene/furan) dye of claim 1, wherein R is C₅～C₉Linear or branched alkoxy or alkyl groups.

3. The poly (triphenylamine-benzothiophene/furan) dye according to claim 1, wherein the group having a conjugated double bond system is one or a combination of conjugated olefin group, conjugated aromatic hydrocarbon group, and heterocyclic group having a conjugated system.

4. The poly (triphenylamine-benzothiophene/furan) dye according to claim 3, wherein the group having a conjugated double bond system is One or a combination of several of them;

wherein,

n≥1；

R₂is hydrogen atom, halogen atom, nitro, hydroxyl, amino, cyano, carboxyl, C₃～C₈Alkoxy group of (C)₃～C₈Alkyl of (C)₃～C₈Alkenyl of (C)₅～C₈Acyl group of (1), C₅～C₇Cycloalkyl of, C₅～C₁₂And one of a five-or six-membered heterocyclic group.

5. The poly (triphenylamine-benzothiophene/furan) dye of claim 1, wherein a is a cyanoacetate group.

6. The poly (triphenylamine-benzothiophene/furan) dye according to claim 1, wherein the molecular weight is 4000 to 30000.

7. The poly (triphenylamine-benzothiophene/furan) dye according to any one of claims 1 to 6, having a structure represented by formula II, formula III or formula IV:

8. the application of the poly (triphenylamine-benzothiophene/furan) dye as claimed in any one of claims 1 to 6, wherein the poly (triphenylamine-benzothiophene/furan) dye is applied to the preparation of dye-sensitized solar cells as a dye layer material.

9. The use of claim 8, wherein the poly (triphenylamine-benzothiophene/furan) dye has a structure represented by formula II, formula III, or formula IV:

10. the use of claim 8, wherein the poly (triphenylamine-benzothiophene/furan) dye is used for preparing a dye layer on the semiconductor nano titanium dioxide layer, the semiconductor nano titanium dioxide and the dye layer together form a light trapping layer, and the light trapping layer is further assembled with a transparent substrate, an electrolyte and a counter electrode to form the dye-sensitized solar cell.