Synthesis and application of photovoltaic material intermediate based on novel fused ring thiophene

Abstract

The invention relates to the field of organic photovoltaic materials, in particular to synthesis and application of a D-A-D type structure organic photovoltaic material intermediate modified by a novel fused ring thiophene as a pi bridge. Alkyl-modified thienopyrrole is used as a pi-bridge electron donating unit (D), and a benzothiadiazole derivative is used as an electron withdrawing group (A). Through a Stille coupling reaction, the organic photovoltaic material intermediate with a D-A-D type structure, which is modified by thienopyrrole as a pi bridge based on undecyl, is obtained. An ultraviolet-visible absorption spectrum test shows that the compound has relatively strong light harvesting capability. The material provided by the invention has good solubility and film-forming property and a wide spectral response range, and is expected to be used as an acceptor material of an organic solar cell.

Description

Technical Field

[0001] The invention relates to the field of organic photovoltaic materials, and in particular to the synthesis and application of a DAD-type structure organic photovoltaic material intermediate modified with a novel condensed ring thiophene as a π bridge. Technical Background

[0002] In 2015, Professor Zhan Xiaowei of Peking University reported the non-fullerene acceptor molecule ITIC with IC as the terminal (Adv. Mater., 2015, 27, 1170). In 2016, Professor Hou Jianhui and Professor Li Yongfang successively reported the work based on ITIC acceptor materials. The device efficiency of polymer / non-fullerene solar cells exceeded 11%. Non-fullerene acceptor materials represented by ITIC system have achieved unprecedented development (Energ. & Enviro. Sci., 2017, 10, 546). In 2017, Hou Jianhui's research group synthesized a new acceptor IT-4F by introducing fluorine atoms at the end of ITIC, and obtained a single-layer device efficiency of more than 13% by blending it with the polymer PBDB-T-SF (J. Am. Chem. Soc., 2017, 139, 7148). In the same year, they introduced an ester side chain into the polymer PBDB-T-SF thiophene bridge and paired it with the receptor IT-4F to obtain the highest efficiency of a single-layer device at that time, 14.5% (J.Am.Chem.Soc., 2018, 140, 7159), which far exceeded the photoelectric conversion efficiency of a single-layer device of a fullerene-based solar cell. In 2018, the research group of Professor Chen Yongsheng of Nankai University and Professor Ye Xuanli of South China University of Technology combined the polymer PTB7-Th with the fullerene PC 71BM and non-fullerene O6T-4F ternary blended active layer, and polymer PBDB-T and non-fullerene FM blended active layer, obtained the highest PCE value of 17.3% for stacked solar cells, setting a new record for solar cell efficiency (Science, 2018, 361, 1094). Until 2019, the research group of Professor Zou Yingping of Central South University reported a photoelectric conversion efficiency of 15.7% based on the new condensed ring acceptor Y6 and polymer donor PM6, breaking the efficiency record of single-layer devices originally held by ITIC and IDT condensed ring systems, and also opening a new era of high-efficiency non-fullerene materials, bringing new breakthroughs in structural design (Joule, 2019, 3, 1). In the same year, Professor Huang Fei's research group at South China University of Technology obtained a single-layer device efficiency value of more than 16% based on the polymer P2F-EHp, and Professor Peng Qiang's research group at Sichuan University obtained a single-layer device efficiency value of more than 16% based on the new polymer Pt-PSFTZ and non-fullerene acceptor Y6 (Adv. Mater., 2019, 1901872). Recently, Professor Ding Liming's research group at the Institute of Nanotechnology, Chinese Academy of Sciences, blended the new polymer D18 with Y6 to form an active layer, and obtained the highest record PCE value of 18.22% for a single-cell solar cell (Sci. Bulletin, 2020, 65, 272).

[0003] Therefore, the new A(π-A')2 type non-fullerene acceptor material is a class of photovoltaic acceptor materials with great development potential. As a non-fullerene acceptor material, it has potential application prospects when matched with suitable medium- and wide-band donor materials. The development and design of new non-fullerene acceptor molecules with high molar absorption coefficient, wide response absorption spectrum, suitable energy level and high carrier mobility is the focus of future organic solar cell development, seeking new breakthroughs in photovoltaic material performance. The implementation of this project is of great significance for revealing the molecular design rules of non-fullerene acceptor molecular materials with excellent performance, obtaining non-fullerene acceptor molecular materials with excellent performance and their solar cell devices. Summary of the invention

[0004] In view of the problems existing in the prior art, we invented a DAD-type organic photovoltaic material intermediate modified with thieno[3,2-b]pyrrole as a π-bridge donor unit. The characteristics of this material are that thieno[3,2-b]pyrrole is a π-bridge unit (D), a benzothiadiazole derivative is an acceptor unit (A), and it is modified with an alkyl chain. The photophysical properties of this DAD-type organic photovoltaic material intermediate were tested, and a new type of photovoltaic material intermediate with a high molar absorption coefficient, a wide response absorption spectrum, and a suitable energy level was developed and designed.

[0005] Therefore, the purpose of the present invention is to provide a novel photovoltaic material intermediate with broad application prospects, which has good solubility and film-forming properties; in photophysical tests, the material has strong light-harvesting ability.

[0006] Based on the classic DA structure, this material introduces the TPyrol-N-C11 unit with a planar condensed ring structure, aiming to achieve a larger charge delocalization range and improve carrier mobility. The design and synthesis of the TPyrol-N-C11 unit are original. The invented TPyrol-N-C11 unit and the small molecule organic photovoltaic material intermediates BTNO-TPy-C11 and BBT-TPy-C11 are conducive to further constructing the molecules of organic photovoltaic materials and their application in solvent-processed bulk heterojunction organic solar cells. The molecular structure and intermediates of this DAD-type structural material can be any of the following molecules.

[0007]

[0008]

[0009] The above-mentioned DAD type organic small molecule photovoltaic material intermediate includes any of the following derivatives:

[0010] A DAD-type organic photovoltaic material intermediate BTNO-TPy-C11 was prepared with 4-undecyl-4H-thieno[3,2-b]pyrrole (TPyrol-N-C11) as the π-bridge donor unit (D) and 5,6-dinitrobenzo[c][1,2,5]thiadiazole (BTNO) as the electron-withdrawing group (A).

[0011] A DAD-type organic photovoltaic material intermediate BBT-TPy-C11 was prepared with 4-undecyl-4H-thieno[3,2-b]pyrrole (TPyrol-N-C11) as the π-bridge donor unit (D) and benzo(bis)thiadiazole (BBT) as the electron-withdrawing group (A).

[0012] The following is a specific synthetic route (see the attached instructions Figure 6 ):

[0013] In order to obtain the above-mentioned material, the synthesis scheme of the present invention is as follows:

[0014] Synthesis of DAD-type small molecule photovoltaic material intermediate TPyrol-NH: 4H-thiophene[3,2-b]pyrrole-5-carboxylic acid ethyl ester reacts with ethylene glycol solution and potassium hydroxide under heating conditions to synthesize the crude product of TPyrol-NH with the ester group removed, and the pure product is obtained by column chromatography separation.

[0015] Synthesis of DAD-type small molecule photovoltaic material intermediate TPyrol-N-C11: The side chain 1-bromoundecyl chain interacts with TPyrol-NH in a dimethylformamide solution with potassium hydroxide. Under heating conditions, an electrophilic substitution reaction occurs to synthesize alkylated TPyrol-N-C11. The crude product is separated by column chromatography to obtain a pure product.

[0016] Synthesis of DAD-type small molecule photovoltaic material intermediate Sn-TPyrol-N-C11: The intermediate TPyrol-N-C11 reacts with n-butyl lithium solution under low temperature conditions to undergo hydrogen extraction reaction, and then reacts with tributyltin chloride to undergo electrophilic substitution reaction to synthesize the intermediate Sn-TPyrol-N-C11.

[0017] Synthesis of the target product BTNO-TPy-C11 of DAD-type small molecule photovoltaic material intermediate: The intermediate Sn-TPyrol-N-C11 and compound 4 undergo a Stille coupling reaction under heating conditions and the catalysis of bistriphenylphosphine palladium dichloride to synthesize the target product BTNO-TPy-C11 of the organic photovoltaic intermediate.

[0018] Synthesis of the target product BBT-TPy-C11 of DAD-type small molecule photovoltaic material intermediate: The intermediate Sn-TPyrol-N-C11 and compound 6 undergo a Stille coupling reaction under heating conditions and the catalysis of bistriphenylphosphine palladium dichloride to synthesize the target product BBT-TPy-C11 of the organic photovoltaic intermediate.

[0019] Compared with most of the disclosed small molecule photovoltaic material intermediates, the DAD type small molecule photovoltaic material intermediate of the present invention has the following characteristics: (1) the introduction of a relatively long flexible alkyl chain 1-undecyl chain for modification makes it easy to adjust the solubility and make the small molecule material have better film-forming property; (2) the use of a novel planar condensed ring thieno[3,2-b]pyrrole as a π bridge unit greatly broadens the spectral absorption range and molar absorption coefficient of the molecule; (3) the use of a novel planar condensed ring thieno[3,2-b]pyrrole as a π bridge unit makes the small molecule material have stronger intermolecular interaction and tighter π-π stacking effect; (4) the existence of donor-acceptor interaction in the molecule forms a strong ICT effect and enhances the charge transfer performance. Therefore, this type of material is a type of organic small molecule photovoltaic material intermediate with great development prospects.

[0020] The application of the present invention is to use the photovoltaic material intermediate designed by the present invention to further synthesize organic photovoltaic non-fullerene acceptor materials, manufacture photovoltaic devices, and realize better conversion of solar energy into electrical energy.

[0021] Description of the drawings

[0022] Figure 1 The molecular structure of TPyrol-NH of the present invention is

[0023] Figure 2 The molecular structure of TPyrol-N-C11 of the present invention is

[0024] Figure 3 The molecular structure of Sn-TPyrol-N-C11 of the present invention is

[0025] Figure 4 The molecular structure of BTNO-TPy-C11 of the present invention is

[0026] Figure 5 The molecular structure of BBT-TPy-C11 of the present invention is

[0027] Figure 6 The specific synthetic route of the present invention is

[0028] Figure 7 The UV-visible absorption spectrum of BTNO-TPy-C11 of the present invention is

[0029] Figure 8 The molecular structure innovation of the material in the present invention DETAILED DESCRIPTION

[0030] The present invention is further described below by means of specific examples, but these specific embodiments do not limit the protection scope of the present invention in any way.

[0031] Example 1

[0032] Synthesis of 4H-thiophene[3,2-b]pyrrole (TPyrol-NH) (see Appendix Figure 1 ):

[0033] Under nitrogen protection, 4H-thiophene [3,2-b] pyrrole-5-carboxylic acid ethyl ester (10g, 51.22mmol) and potassium hydroxide (5.7g, 102.44mmol) were placed in a 250 ml single-mouth bottle. 100 ml of ethylene glycol was added to stir the reaction under light-proof conditions. The reaction solution was heated to 150°C for 3 hours. After the reaction was cooled, the reaction solution was washed three times with a saturated sodium bicarbonate solution, extracted with dichloromethane, and dichloromethane was removed by rotary evaporation. Ethylene glycol was removed by vacuum distillation. The crude product was obtained and used directly in the next step without purification.

[0034] Example 2

[0035] Synthesis of 4-undecyl-4H-thieno[3,2-b]pyrrole (TPyrol-N-C11) (see Appendix Figure 2 ):

[0036] Compound TPyrol-NH (2.46 g, 20 mmol) and 1-bromoundecyl chain (7.06 g, 30 mmol, 1.5 eq) interacted with potassium hydroxide (1.68 g, 30 mmol, 1.5 eq) in dimethylformamide solution. The reaction system repeatedly discharged oxygen and extracted nitrogen three times. The system reacted at 70 ° C for 12 hours. After the reaction stopped, it was poured into water and extracted three times with chloroform. After the organic layer was dried with anhydrous magnesium sulfate, the solvent was evaporated under reduced pressure. The eluent was petroleum ether solution column chromatography purification to obtain a colorless and transparent liquid product TPyrol-N-C11 (5 g, yield: 90%). 1 H NMR (400MHz, CDCl3) δ7.07 (d, J = 4.7Hz, 1H), 6.92 (d, J = 5.2Hz, 1H), 6.85 (d, J = 1.9Hz, 1H), 6.36 (d, J = 2. 8Hz, 1H), 4.02 (t, J = 7.1Hz, 2H), 1.83 (d, J = 6.6Hz, 2H), 1.27 (d, J = 21.7Hz, 16H), 0.88 (t, J = 6.8Hz, 3H).

[0037] Example 3

[0038] Synthesis of 2-(tributyltin)-4-undecyl-4H-thieno[3,2-b]pyrrole (Sn-TPyrol-N-C11) (see Appendix Figure 3 ):

[0039] In a 250mL three-necked flask, dissolve the compound TPyrol-N-C11 (2.78g, 100mmol) in 50mL dry tetrahydrofuran, stir magnetically, slowly add n-butyl lithium (62.5mL, 1.6M, 1eq) at -78℃, and react at -78℃ for 2 hours. Place at -78℃ again and add tributyltin chloride (100mL, 1M, 1eq) at once, and react at room temperature for 5 hours. Pour the reaction solution into 100mL water, extract with dichloromethane three times, 30mL each time, and combine the organic layers. The organic layer is decompressed and dried under vacuum to obtain colorless transparent liquid Sn-TPyrol-N-C11 (5.66g, 90%). 1H NMR (400MHz, CDCl3) δ6.89(s,1H),6.82(d,J=2.9Hz,1H),6.34(d,J=2.8Hz,1H),4.01(t,J=7.1Hz,2H),1.85-1.7 8(m,2H),1.59(dd,J=9.2,6.1Hz,6H),1.31(dd,J=9.8,4.7Hz,13H),1.26(d,J=8.3Hz,18H),0.89-0.85(m,13H).

[0040] Example 4

[0041] 5,6-Dinitro-4,7-di(4-undecyl-4H-thieno[3,2-b]pyrrolyl)benzo[c][1,2,5]thiadiazole (see the attached manual) Figure 4 ):

[0042] Under nitrogen protection, compound 4 (1.92 g, 5 mmol), Sn-TPyrol-N-C11 (2.83 g, 5 mmol), bistriphenylphosphine palladium dichloride (105 mg, 0.15 mmol), and dry toluene (30 mL) were placed in a 100 mL single-mouth bottle. The reaction solution was heated to 80 ° C and reacted overnight. After the reaction stopped and cooled, the solvent was dried under reduced pressure and purified by column chromatography using an eluent (petroleum ether: dichloromethane = 5:1) to obtain solid BTNO-TPy-C11 with a yield of 80%. 1 H NMR (400MHz, CDCl3) δ7.39(s,2H),6.98(d,J=2.9Hz,2H),6.42(d,J=2.8Hz,2H),4.05(dd,J=8.5,5.6Hz,4H),1.87-1.79(m,4H),1.33 -1.24(m,32H),0.87(t,J=6.8Hz,6H).

[0043] Example 5

[0044] 4,7-Di(4-undecyl-4H-thieno[3,2-b]pyrrolyl)benzo(bis)thiadiazole (see the attached manual) Figure 5 ):

[0045] Under nitrogen protection, compound 6 (704 mg, 2 mmol), Sn-TPyrol-N-C11 (1.13 g, 2 mmol), bistriphenylphosphine palladium dichloride (42 mg, 0.06 mmol), and dry toluene (30 mL) were placed in a 100 mL single-mouth bottle. The reaction solution was heated to 80 ° C and reacted overnight. After the reaction stopped and cooled, the solvent was dried under reduced pressure and purified by column chromatography using an eluent (petroleum ether: dichloromethane = 4:1) to obtain solid BBT-TPy-C11 with a yield of 80%. 1 H NMR (400MHz, CDCl3) δ9.08 (s, 2H), 7.01 (d, J = 2.6Hz, 2H), 6.44 (d, J = 2.6Hz, 2H), 4.13 (t,J=7.0Hz,4H),1.99-1.86(m,4H),1.31(d,J=50.4Hz,32H),0.86(t,J=6.7Hz,6H).

[0046] Example 6

[0047] Characterization of DAD-based small molecule photovoltaic materials and testing of their light absorption properties

[0048] DAD-type small molecule photovoltaic materials 1 The H NMR spectrum was measured by a Bruker Dex-400 NMR instrument, and the UV-visible absorption spectrum was measured by a HP-8453 UV-visible spectrometer.

[0049] Example 7

[0050] BTNO-TPy-C11 light absorption performance (see the attached manual Figure 7 ):

[0051] Although the present invention has been described in conjunction with the preferred embodiments, the present invention is not limited to the above embodiments, and it should be understood that the appended claims summarize the scope of the present invention. Under the guidance of the inventive concept, those skilled in the art should be aware that certain changes made to the various embodiments of the present invention will be covered by the spirit and scope of the claims of the present invention.

Claims

1. Synthesis and application of a DAD-type organic photovoltaic material intermediate modified with thieno[3,2-b]pyrrole as a π bridge, characterized in that Its structural formula is shown in Formula I. Wherein, the electron-withdrawing bridging group A is selected from one of the following structures:

2. The DAD-type organic photovoltaic material intermediate modified with thieno[3,2-b]pyrrole as π bridge according to claim 1, characterized in that: The characteristics of this type of material are that it uses 4-undecyl-4H-thieno[3,2-b]pyrrole as the π bridge unit (D) and a benzothiadiazole derivative as the acceptor unit (A). The photophysical properties of this DAD-type organic photovoltaic material intermediate were tested, and a new type of photovoltaic material intermediate with a high molar absorption coefficient, a wide response absorption spectrum, and a suitable energy level was developed and designed.

3. The DAD-type organic photovoltaic material intermediate modified with thieno[3,2-b]pyrrole as π bridge according to claim 1, characterized in that: The electron-withdrawing bridge acceptor A unit is dinitrobenzothiadiazole, benzobithiadiazole, benzothiadiazole, monofluorobenzothiadiazole, bisfluorobenzothiadiazole, and bisoctyloxybenzothiadiazole.

4. The DAD-type organic photovoltaic material intermediate modified with thieno[3,2-b]pyrrole as π bridge according to any one of claims 1 to 3, characterized in that: The introduction of a planar condensed ring structure of 4-undecyl-4H-thieno[3,2-b]pyrrole unit aims to achieve a larger charge delocalization range and improve carrier mobility, which is conducive to further constructing the molecules of organic photovoltaic materials and their application in solvent-processed bulk heterojunction organic solar cells.

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