Broad-band-gap conjugated polymer donor material and preparation method and application thereof

Abstract

The invention belongs to the technical field of solar cells, and particularly relates to a wide-band-gap conjugated polymer donor material and a preparation method and application thereof. The average molecular weight of the wide-band-gap conjugated polymer donor material is 20000-100000, and the wide-band-gap conjugated polymer donor material is blended with a narrow-band-gap non-fullerene small molecule receptor to construct an organic solar cell. And the photoelectric conversion efficiency of the organic solar cell can be up to 19.56%. An organic solar cell based on BLZ-19 is one of the highest two components at present. The synthesis method is simple, conditions are easy to realize, and large-scale popularization can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of solar cells, and in particular relates to a wide bandgap conjugated polymer donor material and a preparation method and application thereof. Background Art

[0002] Organic solar cells have been one of the focuses of academic and industrial attention in recent years due to their many advantages, such as light weight, flexibility, wide sources of raw materials, and large-area processing. Among various organic solar cells, polymer organic solar cells have developed most rapidly in recent years with the development of DA-type copolymers. Compared with polymer donors, organic small molecule donor materials have a certain molecular structure, no batch differences during the synthesis process, and better crystallinity, which is beneficial to improving the mobility of carriers. However, excessive crystallinity will affect the phase separation scale of the active layer due to excessive aggregation, which will make the phase region discontinuous to a certain extent, thereby affecting the effective separation of excitons and the transfer of charges.

[0003] Polymer donor materials can generally change the structure of the main chain, side chain and π bridge to regulate photovoltaic performance. Among them, alkyl side chains are particularly important for the self-assembly ability of polymer materials with the same skeleton, so they have a significant impact on the performance of polymer solar cells. Compared with linear side chains, branched side chains can greatly improve photovoltaic performance. They have a great impact on absorption spectra, energy levels, film morphology, and charge transfer characteristics. Therefore, to a certain extent, they play a great role in improving the photoelectric conversion efficiency of batteries.

[0004] The combination of wide bandgap conjugated polymers as donor materials and narrow bandgap small molecules as acceptor materials can currently achieve a photoelectric conversion efficiency close to 20%. However, the types of high-performance wide bandgap polymers that are widely used are limited, such as PM6 with thienothiophene dione as the building block and D18 with dithienobenzothiadiazole as the building block. Therefore, there is an urgent need to develop new polymer donor materials. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a wide bandgap conjugated polymer donor material and a preparation method and application thereof, design and synthesize a new wide bandgap polymer donor material, and blend it with a narrow bandgap non-fullerene small molecule acceptor to construct an organic solar cell.

[0006] The technical solutions adopted are:

[0007] A wide bandgap conjugated polymer donor material, the structure of which is shown below:

[0008]

[0009] Wherein, Ar1 is an aromatic structure, R, R1, and R2 are C4-C20 alkyl chain, X is H, F or Cl, and n is the average degree of polymerization; the average molecular weight of the donor material is between 20,000 and 100,000.

[0010] Preferably, Ar1 is any of the following structures:

[0011]

[0012] R, R1, and R2 are branched or straight chain groups.

[0013] A method for preparing a wide bandgap conjugated polymer donor material comprises the following steps:

[0014] (1) First, esterify the dibrominated thiophene carboxylic acid to generate compound 1:

[0015]

[0016] (2) Compound 1 reacts with an organoboron reagent or an organotin reagent under the action of a catalyst to obtain compound 2:

[0017]

[0018] (3) Compound 2 is oxidized under the action of FeCl3 or DDQ to obtain compound 3:

[0019]

[0020] (4) Compound 3 is subjected to bromination reaction with NBS or liquid bromine to obtain compound 4:

[0021]

[0022] (5) Compound 4 reacts with a thiophene tin reagent or a thiophene boron reagent in the presence of a catalyst to obtain compound 5:

[0023]

[0024] (6) Compound 5 reacts with NBS or liquid bromine to obtain monomer 1 after bromination:

[0025]

[0026] (7) Monomer 1 and monomer 2 are dissolved in an organic solvent with a catalyst, and a polymerization reaction is carried out under nitrogen protection to obtain the donor material. The reaction is as follows:

[0027]

[0028] Preferably, in the step (1), R1OH is dissolved in dichloromethane under the action of dicyclohexylcarbodiimide and 4-dimethylaminopyridine and stirred at room temperature to obtain compound 1.

[0029] Preferably, in step (2), the organotin or organoboron reagent is 3-(tributyltinalkyl)thiophene or thiophene-3-boronic acid pinacol ester; when the organotin reagent is selected, the reaction solvent is toluene, the reaction temperature is between 90 and 150°C, and the catalyst is tetrakis(triphenylphosphine)palladium; when the organoboron reagent is selected, the reaction solvent is a mixed solvent of tetrahydrofuran and water in a ratio of 10 to 1:1; the base is sodium bicarbonate, the catalyst is tetrakis(triphenylphosphine)palladium, and the reaction temperature is between 50 and 100°C.

[0030] The organotin reagent used in step (5) is the same as the organotin reagent used in step (2), the preferred catalyst is tetrakistriphenylphosphine palladium, the reaction solvent is toluene, and the reaction temperature is 80-130°C.

[0031] Preferably, in step (3), ferric chloride is used as a catalyst, the reaction solvent is a mixture of nitromethane and dichloromethane, and the reaction temperature is room temperature.

[0032] Preferably, in step (4), the reaction solvent is chloroform and the reaction temperature is room temperature.

[0033] Preferably, in step (6), the reaction solvent is DMF, and the reaction is carried out at room temperature.

[0034] Preferably, in step (7), monomer 2 is: (4,8-bis(5-(2-ethylhexyl)-4-fluorothiophene-2-yl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)bis(trimethylstannane), the catalyst is Pd2(dba)3, the solvent used in the reaction is toluene, and the reaction temperature is 80-130°C.

[0035] An application of a wide bandgap conjugated polymer donor material, characterized in that an organic solar cell device is prepared; the organic solar cell device comprises an anode, a hole transport layer, an active layer material, an electron transport layer and a cathode, the active layer material comprises an electron donor and an electron acceptor, wherein the electron donor is the donor material, at least one or a combination of two; the electron acceptor is a narrow bandgap small molecule acceptor or a polymer acceptor; the mass ratio of the electron donor to the electron acceptor is between 1:3 and 3:1. For example, it can be 1:3, 1:2.5, 1:2, 1:1.5, 1:1, 1.5:1, 2:1, 2.5:1 or 3:1, etc.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The photoelectric conversion efficiency of the organic solar cell prepared by using the wide bandgap conjugated polymer donor material of the present invention is as high as 19.56%. The organic solar cell based on BLZ-19 is one of the highest binary devices at present.

[0038] The synthesis route of the invention is simple, the conditions are easy to achieve, and it can be promoted on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is the H-NMR spectrum of compound 1 synthesized in Example 1 of the present invention.

[0040] Figure 2 This is the H-NMR spectrum of compound 2 synthesized in Example 1 of the present invention.

[0041] Figure 3 This is the H-NMR spectrum of compound 3 synthesized in Example 1 of the present invention.

[0042] Figure 4 This is the H-NMR spectrum of compound 4 synthesized in Example 1 of the present invention.

[0043] Figure 5 This is the H-NMR spectrum of compound 5 synthesized in Example 1 of the present invention.

[0044] Figure 6 This is the H-NMR spectrum of monomer 1 synthesized in Example 1 of the present invention.

[0045] Figure 7 This is the ultraviolet absorption spectrum of BLZ-19 prepared in the present invention.

[0046] Figure 8 This is the JV curve of the device based on BZL-19 of the present invention. DETAILED DESCRIPTION

[0047] The accompanying drawings are for illustrative purposes only. The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments. Unless otherwise specified, the chemical substances, instruments, etc. used in the present invention can be obtained through conventional commercial channels.

[0048] Example 1

[0049] i. Synthesis of Compound 1:

[0050] 2-Ethylhexanol (1.95 g, 15 mmol) was added to a mixture of 4,5-dibromothiophene-2-carboxylic acid (4.29 g, 15 mmol), DCC (3.09 g, 15 mmol), and DMAP (0.18 g, 1.5 mmol) in CH2Cl2 (60 mL). The mixture was stirred at room temperature for 18 h. The reaction solution was then poured into water and extracted with dichloromethane three times. The organic phases were combined and dried over anhydrous magnesium sulfate. The solvent was removed under reduced pressure, and the crude product was purified by column chromatography to obtain compound 1 as a yellow oil (4.96 g, 83%).

[0051] like Figure 1 As shown, the H NMR spectrum of compound 1 shows that 1 H NMR (400MHz, Chloroform-d) δ7.56 (s, 1H), 4.19 (d, J = 5.7Hz, 2H), 1.76–1.68 (m, 1H), 1.32 (dd, J = 9.5, 5.3Hz, 8H), 0.89 (d, J = 7.4Hz, 6H).

[0052] ii. Synthesis of Compound 2:

[0053] Compound 1 (4 g, 10.05 mmol), thiophene-3-ylboronic acid (3.6 g, 28.14 mmol) and potassium carbonate (4.16 g, 30.15 mmol) were dissolved in THF (60 mL) and H2O (8 mL), and vacuumed and filled with nitrogen three times continuously. Then Pd(PPh3)4 (200 mg) was added, and vacuumed and filled with nitrogen for three more times. The mixture was refluxed at 80°C overnight, the solvent was removed under reduced pressure, extracted with DCM, and washed with saturated NaCl solution. The solvent was removed under reduced pressure to obtain a crude product. Column chromatography gave a yellow oil (4.06 g) with a yield of 86%.

[0054] like Figure 2 As shown, the H NMR spectrum of compound 2 shows that 1 H NMR(600MHz,Chloroform-d)δ7.79(s,1H),7.30(t,J=3.2Hz,3H),7.21(d,J=2.9Hz,1H),7.03–6.98(m,2H),4.23(t,J=6.2Hz, 2H),1.72-1.68(m,1H),1.46-1.42(m,2H),1.40-1.36(m,2H),1.35-1.31(m,4H),0.95(t,J=7.5Hz,3H),0.91(t,J=6.9Hz,3H).

[0055] iii. Synthesis of Compound 3:

[0056] Compound 2 (2 g, 4.94 mmol) was dissolved in DCM (50 mL) and vacuumed and nitrogen-filled for 3 cycles. Then, FeCl3 (2 g) was added and vacuumed and nitrogen-filled for 3 cycles. The reaction was allowed to react at room temperature for 2 hours. After the reaction was completed, 100 mL of water was added to quench the reaction, extracted with DCM, and washed with saturated NaCl solution. The solvent was removed under reduced pressure to obtain a crude product. Column chromatography gave a white solid (1.45 g) with a yield of 73%.

[0057] like Figure 3 As shown, the H NMR spectrum of compound 3 shows that 1 H NMR(600MHz,Chloroform-d)δ8.40(s,1H),7.73(d,J=5.3Hz,1H),7.60(d,J=5.4Hz,1H),7.52(dd,J=5.3,2.4Hz,2H),4.32(t,J=5.8Hz,2H),1.79 -1.76(m,1H),1.55–1.49(m,2H),1.47–1.43(m,2H),1.41–1.34(m,4H),1.00(t,J=7.5Hz,3H),0.94(t,J=7.0Hz,3H).

[0058] iv. Synthesis of Compound 4:

[0059] NBS (1.11 g, 6.26 mmol) in 20 mL CHCl3 was added dropwise to a CHCl3 solution of compound 3 (1.2 g, 2.98 mmol) at 0°C. The reaction was allowed to react for 10 h in the dark. After the reaction was completed, the reaction was quenched with an aqueous sodium sulfite solution, extracted three times with DCM, and dried over anhydrous MgSO4. After filtration, the organic solvent was removed under reduced pressure. The obtained compound 4 did not need to be further purified to obtain compound 4 (1.58 g, yield: ~95%) as a white solid.

[0060] like Figure 4 As shown, the H NMR spectrum of compound 4 shows that 1 H NMR(600MHz,Chloroform-d)δ8.31(s,1H),7.72(s,1H),7.60(s,1H),4.33–4.29(m,2H),1.79-1.75(m,1H ),1.52-1.48(m,2H),1.45–1.42(m,2H),1.38–1.35(m,4H),0.99(t,J=7.5Hz,3H),0.93(t,J=6.9Hz,3H).

[0061] v. Synthesis of Compound 5:

[0062] Compound 4 (1 g, 1.79 mmol) and trialkyl (4-(2-ethylhexyl) thiophene-2-yl) stannane (2.17 g, 4.48 mmol) were dissolved in toluene (30 mL), and then vacuumed and nitrogen-filled for 3 consecutive cycles. Then, Pd(PPh3)4 (80 mg) was added, and vacuumed and nitrogen-filled for 3 consecutive cycles. The mixture was refluxed at 110°C overnight. After cooling to room temperature, it was extracted with dichloromethane and dried over anhydrous MgSO4. After removing the solvent, the product was purified by column chromatography to obtain a yellow oil (1.07 g, yield: ~76%).

[0063] like Figure 5 As shown, the H NMR spectrum of compound 5 shows that 1 H NMR(600MHz,Chloroform-d)δ8.42(s,1H),7.77(s,1H),7.61(s,1H),7.17(s,2H),6.91(s,2H),4.34–4.29(m,2H), 2.57(s,4H),1.81–1.75(m,1H),1.65–1.60(m,8H),1.38-1.31(m,18H),1.00(t,J=7.5Hz,3H),0.94-0.90(m,15H).

[0064] vi. Synthesis of Monomer 1:

[0065] Compound 5 (800 mg, 1.01 mmol) was dissolved in DMF, and then NBS (368 mg, 2.07 mmol) was slowly added to react for 2 hours in the dark. After the reaction was completed, 100 mL of water was added, extracted three times with DCM, dried over anhydrous magnesium sulfate, and the organic solvent was removed under reduced pressure. The product was purified by column chromatography to obtain a yellow solid (796 g, yield: ~83%).

[0066] like Figure 6 As shown, the nuclear magnetic hydrogen spectrum of monomer 1 shows that 1 H NMR(600MHz,Chloroform-d)δ8.35(s,1H),7.64(s,1H),7.50(s,1H),6.99(s,2H),4.36–4.20(m,2H),2.52(d,J= 7.3Hz, 4H), 1.81–1.74 (m, 1H), 1.70–1.63 (m, 2H), 1.39–1.29 (m, 22H), 1.00 (t, J = 7.5Hz, 3H), 0.95–0.90 (m, 15H).

[0067] vii. Synthesis of BLZ-19:

[0068] Compound 6 (100 mg, 0.105 mmol), (4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)bis(trimethyltin) (98.75 mg, 0.105 mmol), Pd2(dba)3 (3.0 mg, 0.0033 mmol) and P(o-Tol)3 (10.1 mg, 0.033 mmol) in toluene (3 mL) were refluxed in a sealed tube for 16 h. After cooling to room temperature, the reaction mixture was added dropwise to 100 mL of methanol to form a precipitate. The crude product was purified by Soxhlet extraction with a series of solvents such as acetone, dichloromethane and chloroform. A purple solid BLZ-19 (119 mg) was obtained.

[0069] The synthetic chemical formula is:

[0070]

[0071] like Figure 7 As shown, in the solution state, the absorption range of the polymer BLZ-19 is 430-610nm; while in the film state, the absorption range of the polymer BLZ-19 is 400-610nm, and the maximum absorption wavelength is relatively red-shifted. At the same time, in the solution and film states, the absorption of the polymer has a shoulder peak, which indicates that the polymer has formed a certain aggregation.

[0072] The polymer of Example 1 and L8-BO were used as the active layer of the organic solar cell, and the open circuit voltage of the organic solar cell was measured to be 0.920-0.922 V (see Figure 2 As shown), the short-circuit current density is 26.93~27.02mA / cm 2 , the filling factor is 77.82-78.08%, and the photoelectric conversion efficiency is 19.22-19.56%. The energy conversion efficiency of this organic solar cell is very high, and the organic solar cell based on BLZ-19 is one of the highest binary devices currently.

[0073] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A wide bandgap conjugated polymer donor material, characterized in that: Its structure is as follows: Wherein, Ar1 is an aromatic structure, R, R1, and R2 are C4-C 20 alkyl chain, X is H, F or Cl, and n is the average degree of polymerization; the average molecular weight of the donor material is 20,000 to 100,000.

2. A wide bandgap conjugated polymer donor material according to claim 1, characterized in that: Ar1 is any of the following structures: R, R1, and R2 are branched or straight chain groups.

3. The method for preparing a wide bandgap conjugated polymer donor material according to any one of claims 1 or 2, characterized in that: The steps include: (1) First, esterify the dibrominated thiophene carboxylic acid to generate compound 1: (2) Compound 1 reacts with an organoboron reagent or an organotin reagent under the action of a catalyst to obtain compound 2: (3) Compound 2 is oxidized under the action of FeCl3 or DDQ to obtain compound 3: (4) Compound 3 is subjected to bromination reaction with NBS or liquid bromine to obtain compound 4: (5) Compound 4 reacts with a thiophene tin reagent or a thiophene boron reagent in the presence of a catalyst to obtain compound 5: (6) Compound 5 reacts with NBS or liquid bromine to obtain monomer 1 after bromination: (7) Monomer 1 and monomer 2 are dissolved in an organic solvent with a catalyst, and a polymerization reaction is carried out under nitrogen protection to obtain the donor material. The reaction is as follows:

4. The method for preparing a wide bandgap conjugated polymer donor material according to claim 3, characterized in that: In the step (1), R1OH is dissolved in dichloromethane under the action of dicyclohexylcarbodiimide and 4-dimethylaminopyridine and stirred at room temperature to obtain compound 1.

5. The method for preparing a wide bandgap conjugated polymer donor material according to claim 3, characterized in that: In the step (2), the organotin or organoboron reagent is 3-(tributyltinalkyl)thiophene or thiophene-3-boronic acid pinacol ester; when the organotin reagent is selected, the reaction solvent is toluene, the reaction temperature is between 90 and 150° C., and the catalyst is tetrakis(triphenylphosphine)palladium; when the organoboron reagent is selected, the reaction solvent is a mixed solvent of tetrahydrofuran and water in a ratio of 10 to 1:1; the base is sodium bicarbonate, the catalyst is tetrakis(triphenylphosphine)palladium, and the reaction temperature is between 50 and 100° C.

6. The method for preparing a wide bandgap conjugated polymer donor material according to claim 3, characterized in that: In the step (3), ferric chloride is used as a catalyst, the reaction solvent is a mixture of nitromethane and dichloromethane, and the reaction temperature is room temperature.

7. The method for preparing a wide bandgap conjugated polymer donor material according to claim 3, characterized in that: In the step (4), the reaction solvent is chloroform and the reaction temperature is room temperature.

8. The method for preparing a wide bandgap conjugated polymer donor material according to claim 3, characterized in that: In the step (6), the reaction solvent is DMF, and the reaction is carried out at room temperature.

9. The method for preparing a wide bandgap conjugated polymer donor material according to claim 3, characterized in that: In the step (7), monomer 2 is: (4,8-bis(5-(2-ethylhexyl)-4-fluorothiophene-2-yl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)bis(trimethylstannane), the catalyst is Pd2(dba)3, the solvent used in the reaction is toluene, and the reaction temperature is 80 to 130°C.

10. Use of a wide bandgap conjugated polymer donor material prepared as claimed in claim 1-2 or 3-9, characterized in that: An organic solar cell device is prepared; the device of the organic solar cell comprises an anode, a hole transport layer, an active layer material, an electron transport layer and a cathode, the active layer material comprises an electron donor and an electron acceptor, wherein the electron donor is the donor material, at least one or a combination of two; the electron acceptor is a narrow bandgap small molecule acceptor or a polymer acceptor; the mass ratio of the electron donor to the electron acceptor is between 1:3 and 3:1.

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