An A-D-A type indacenodithiophene planar conjugated derivative, its preparation method and application

Abstract

The present invention relates to the field of conjugated molecules, and discloses an A-D-A type indacenodithiophene planar conjugated derivative, a preparation method thereof and an application thereof. The present invention creatively designs and synthesizes an A-D-A type indacenodithiophene planar conjugated derivative, uses an indacenodithiophene unit as the molecular center, introduces benzodithiophene as a π-bridge structure to regulate its light absorption, and connects an electron-withdrawing group at the end to promote carrier transport. The A-D-A type indacenodithiophene planar conjugated derivative is used as an additive for the active layer of an organic solar cell, has good light absorption complementarity with currently high-performance active layer materials, and at the same time has good charge transport characteristics and appropriate electron energy levels. The indacenodithiophene conjugated derivative synthesized by the present invention has reasonable energy levels and good light absorption ability, and can effectively improve the short-circuit current and photoelectric conversion efficiency of an organic solar cell.

Description

Technical Field

[0001] The present invention relates to the field of conjugated molecules, and more specifically, to an A-D-A type indacenodithiophene planar conjugated derivative, a preparation method thereof, and an application thereof. Background Art

[0002] Exploring and developing clean and renewable energy based on solar energy is one of the keys to achieving the "dual carbon" goal and promoting the green and high-quality development of social economy. A solar cell is a device that directly converts solar energy into electrical energy and is one of the most effective ways to utilize solar energy. Among them, organic solar cells have attracted much attention in recent years due to their advantages such as simple process, low cost, light weight, and flexibility. Currently, the efficiency of single-junction organic solar cells prepared based on polymer donors and non-fullerene small molecule acceptors has exceeded 19%, showing great development prospects and application values.

[0003] The active layer of an organic solar cell is an important part for realizing photoelectric conversion. How to improve the optical absorption characteristics and electrical transport ability of the active layer is the key to achieving high-efficiency organic solar cells. Currently, A-D-A type conjugated molecules with multi-ring conjugated units as the core and electron-withdrawing units at the ends have shown excellent performance in organic solar cell acceptors due to their adjustable light absorption and excellent electron transport properties. In particular, they can be introduced as the third component into the active layer to enhance the light absorption ability of the active layer at the same time.

[0004] The prior art discloses a D(A1-π-A2)2 type conjugated small molecule based on a diarylindacene fused ring unit and a preparation method thereof. The conjugated small molecule uses a diarylindacene fused ring with a rigid planar structure as the electron-donating (D) unit and thiophene as the π-bridge unit. By selecting and matching different electron-withdrawing groups A1 and A2, a series of narrow-bandgap small molecule photoactive layer materials that can absorb near-infrared light are constructed.

[0005] The prior art discloses an A-D-A conjugated molecule and a preparation method thereof, an organic solar cell, and an application of the A-D-A conjugated molecule in an organic solar cell. The end-capping group EG of the A-D-A conjugated molecule based on a heptacene fused ring unit has a strong electron-withdrawing ability, and the A-D-A conjugated molecule contains a large conjugated planar structure with a B←N bond, which is suitable for use as an electron acceptor material in the preparation of organic solar cells.

[0006] The prior art discloses an A-D-A conjugated molecule based on a thiophenocyclopentadione derivative and a preparation method thereof. A class of A-D-A conjugated molecules with thiophenocyclopentadione derivatives as end-capping groups, homo-pentatomic aromatic heterocycles as bridging units, and polycyclic ladder conjugated molecules as the core, a preparation method thereof, and the application of such molecules as active layer electron acceptor materials in organic solar cells (OPVs) are disclosed.

[0007] However, the light absorption complementarity between existing A-D-A type molecular materials and the photosensitive active layer is generally poor, which limits their practical applications. Summary of the Invention

[0008] To solve the technical defects that the light absorption complementarity between existing A-D-A type molecular materials and the photosensitive active layer is generally poor, and the light absorption complementarity between the third component additive and the organic battery active layer is low, the present invention provides an A-D-A type indacenodithiophene planar conjugated derivative. The A-D-A type indacenodithiophene planar conjugated derivative is used as an additive for the active layer of an organic solar cell, has good light absorption complementarity with currently high-performance active layer materials, and at the same time has good charge transport characteristics and appropriate electron energy levels.

[0009] Another object of the present invention is to provide a preparation method of an A-D-A type indacenodithiophene planar conjugated derivative;

[0010] Another object of the present invention is to provide an application of an A-D-A type indacenodithiophene planar conjugated derivative;

[0011] Another object of the present invention is to provide an organic solar cell.

[0012] To solve the above technical problems, the technical solution of the present invention is as follows:

[0013] An A-D-A type indacenodithiophene planar conjugated derivative, the chemical structural formula of which is shown as follows:

[0014]

[0015] Wherein R 1 is selected from straight-chain or branched-chain alkyl groups of C 1 to C 20 , R 2 is selected from straight-chain or branched-chain alkyl groups of C 1 to C 6 , and R 3 is selected from straight-chain or branched-chain alkyl groups of C 1 to C 6 .

[0016] Further, R 1 is selected from straight-chain or branched-chain alkyl groups of C16; R 2 , R 3 are selected from straight-chain or branched-chain alkyl groups of C2 or C4.

[0017] A preparation method of the above-mentioned A-D-A type indacenodithiophene planar conjugated derivative, comprising the following steps:

[0018] S1. Under an inert atmosphere, benzothieno[3,2-b]thiophene-2,6-dione undergoes a substitution reaction with compound A to obtain compound B.

[0019] The structural formula of compound A is: wherein R 2 is selected from straight-chain or branched alkyl groups of C 1 ~C 6 , and R 3 is selected from straight-chain or branched alkyl groups of C 1 ~C 6 .

[0020] The structural formula of compound B is: wherein R 2 is selected from straight-chain or branched alkyl groups of C 1 ~C 6 , and R 3 is selected from straight-chain or branched alkyl groups of C 1 ~C 6 .

[0021] S2. Under an inert atmosphere, compound B obtained in step S1 undergoes a substitution reaction with N-bromosuccinimide to obtain compound C;

[0022] The structural formula of compound C is: wherein R 2 is selected from straight-chain or branched alkyl groups of C 1 ~C 6 , and R 3 is selected from straight-chain or branched alkyl groups of C 1 ~C 6 .

[0023] S3. Under an inert atmosphere, compound C obtained in step S2 undergoes a Vilsmeier-Haack reaction under the action of N,N-dimethylformamide and phosphorus oxychloride to form compound D.

[0024] The structural formula of compound D is: wherein R 2 is selected from straight-chain or branched alkyl groups of C 1 ~C 6 , and R 3 is selected from straight-chain or branched alkyl groups of C 1 ~C 6 .

[0025] S4. Compound D obtained in step S3 and compound E undergo a Suzuki coupling reaction under the catalysis of a palladium catalyst to obtain compound F.

[0026] The structural formula of compound E is: wherein R1 Selected from C 1 ~C 20 linear or branched alkyl groups.

[0027] The structural formula of compound F is: In the formula, R1 is selected from linear or branched alkyl groups of C1~C20, R2 is selected from linear or branched alkyl groups of C1~C6, and R3 is selected from linear or branched alkyl groups of C1~C6.

[0028] S5. React compound F obtained in step S4 with compound G through Knoevenagel condensation reaction to obtain an A-D-A type indacenodithiophene planar conjugated derivative.

[0029] The structural formula of compound G is:

[0030] Furthermore, the molar ratio of benzo[1,2-b:4,5-b']dithiophene-4,8-dione to compound A in step S1 is 1:2~3.

[0031] Furthermore, the molar ratio of compound B to N-bromosuccinimide in step S2 is 1:0.9~1.1.

[0032] Furthermore, the reaction temperature of step S2 is 0~5℃.

[0033] Furthermore, the reaction temperature of step S3 is 0~10℃.

[0034] Furthermore, the molar ratio of compound D to compound E in step S4 is 2~3:1.

[0035] Furthermore, the molar ratio of compound F to compound G in step S5 is 2~3:1.

[0036] An application of the A-D-A type indacenodithiophene planar conjugated derivative in an organic solar cell, which is used to prepare an active layer of an organic solar cell or as an active layer material.

[0037] The A-D-A type indacenodithiophene planar conjugated derivative has a good planar shape. By using the rigid planar structure of the indacenodithiophene fused ring unit and the intramolecular non-bonding "conformational lock", a planar molecular structure is formed, which can effectively promote the stacking between molecules in the active layer and promote the transport of carriers. The A-D-A type indacenodithiophene planar conjugated derivative is soluble in common organic solvents such as chloroform and chlorobenzene, and can be added in a small amount to the active layer solution to prepare the active layer of an organic solar cell.

[0038] An organic solar cell, the battery device includes an active layer; the active layer is prepared from the A-D-A type indacenodithiophene planar conjugated derivative or by using the A-D-A type indacenodithiophene planar conjugated derivative as a material.

[0039] The organic solar cell device includes an ITO glass, an anode modification layer, an active layer, a cathode modification layer and an electrode which are stacked in sequence from bottom to top. The active layer contains an A-D-A type indacenodithiophene planar conjugated derivative as an active layer additive.

[0040] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0041] The A-D-A type indacenodithiophene planar conjugated derivative of the present invention has a brand-new molecular structure. By using different molecular central nuclei, heterogeneous π-bridge structures and electron-withdrawing units, the main peak of light absorption can be adjusted to 700 nm to varying degrees; with different π-bridge structures, its secondary peak of light absorption can be adjusted to 450 nm. More importantly, the A-D-A type indacenodithiophene planar conjugated derivative provided by the present invention has an extremely suitable absorption spectrum and light absorption characteristics that are completely complementary to the existing active layer materials. This molecule has reasonable energy levels and good light absorption ability, and shows excellent light absorption complementarity with existing high-performance active layer materials (such as PM6, D18, Y6, L8-BO), and is suitable as an active layer additive for preparing organic solar cells. At the same time, the A-D-A type indacenodithiophene planar conjugated derivative provided by the present invention uses C-H…O and S…O non-covalent conformational locks to construct a molecular skeleton with high planarity, which is the molecule with the highest planarity among existing A-D-A type conjugated derivatives. This planar structure is beneficial to promoting π-π stacking between molecules and improving the carrier transport efficiency between molecules. The synthesis of the A-D-A type indacenodithiophene planar conjugated derivative of the present invention can effectively improve the short-circuit current and photoelectric conversion efficiency of organic solar cells. Description of the Drawings

[0042] Figure 1 is the ultraviolet-visible absorption spectrum of the A-D-A type indacenodithiophene planar conjugated derivative;

[0043] Figure 2 is the top view of the molecular optimal conformation of the A-D-A type indacenodithiophene planar conjugated derivative calculated by DFT (B3LYP / 6-311G(d,p));

[0044] Figure 3 is the side view of the molecular optimal conformation of the A-D-A type indacenodithiophene planar conjugated derivative calculated by DFT (B3LYP / 6-311G(d,p));

[0045] Figure 4 It is a schematic diagram of the battery structure of a solar cell;

[0046] Figure 5 It is the external quantum efficiency curve of a solar cell;

[0047] Figure 6 It is the J-V curve of a solar cell. Specific implementation manners

[0048] The present invention will be further described below in conjunction with the accompanying drawings of the specification and specific embodiments, but the embodiments do not impose any form of limitation on the present invention. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0049] Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0050] Example 1

[0051] The structural formula of the A-D-A type indacenodithiophene planar conjugated derivative IDT-BDT-IC of the present invention is as follows:

[0052]

[0053] The specific synthesis steps are as follows:

[0054] 1) Weigh 16 molar equivalents of benzo[1,2-b:4,5-b']dithiophene-4,8-dione and mix it with 250 molar equivalents of sodium hydroxide in a three-necked round-bottom flask. Add 60 molar equivalents of deionized water to dissolve it. Under an argon atmosphere, reflux with condensation at 105°C for 1 hour. Add 430 molar equivalents of zinc powder. After continuously stirring at 105°C for 1 hour, add 3.73 molar equivalents of TABA and 40 mmol molar equivalents of 2-bromo-2-methylpropane. Reflux with condensation at 105°C for 12 hours. After the reaction is completed, pour in 70 molar equivalents of deionized water, extract 3 times with 100 molar equivalents of dichloromethane, and use petroleum ether and dichloromethane as the eluent. Purify by column chromatography separation to obtain 12.69 mmol of intermediate compound molecule 1, with a yield of 79.31%. MS(M + ): 446.83; 1 HNMR(400 MHz, CDCl 3 ), δ(ppm): 7.98(d, 2H, J = 8.26 Hz), 7.88(d, 2H, J = 8.38 Hz), 3.98 - 3.95(m, 4H), 1.84 - 1.81(m, 2H), 1.56 - 1.52(m, 4H), 1.32 - 1.24(m, 12H), 0.88 - 0.73(m, 12H). The synthesis route is as follows:

[0055]

[0056] 2) Weigh 12.6 molar equivalents of intermediate compound 1 into a three-necked round-bottom flask, add 100 molar equivalents of chloroform and 50 molar equivalents of acetic acid. After cooling the solution to 0 °C, add 12.4 molar equivalents of N-bromosuccinimide, stir evenly under an argon atmosphere, and react at low temperature in the dark for 3 hours. After the reaction is completed, add sodium hydroxide to adjust the pH value of the solution to neutral, then wash it 3 times with deionized water, and extract it 3 times with dichloromethane. Use petroleum ether and dichloromethane as the eluent and purify it by column chromatography to obtain 4.17 molar equivalents of intermediate compound 2, yield: 1 HNMR(400MHz,CDCl 3 ), δ(ppm): 7.94(d, 1H, J = 8.42Hz), 7.90(d, 1H, J = 8.42Hz), 7.21(s, 1H), 4.02 - 3.99(m, 4H), 1.88 - 1.85(m, 2H), 1.58 - 1.55(m, 4H), 1.29 - 1.22(m, 12H), 0.91 - 0.81(m, 12H). The synthetic route is as follows:

[0057]

[0058] 3) Weigh 4 molar equivalents of intermediate compound 2 into a three-necked round-bottom flask, add 60 molar equivalents of 1,2-dichloroethane and 8 molar equivalents of N,N-dimethylformamide, stir for 20 minutes under an argon atmosphere, then add 9 molar equivalents of phosphorus oxychloride, stir for 1 hour, and then carry out reflux condensation at 90 °C for 24 hours. After the reaction is completed, add sodium hydroxide to adjust the pH value of the solution to neutral, then extract it 3 times with dichloromethane. Use petroleum ether and dichloromethane as the eluent and purify it by column chromatography to obtain 2 molar equivalents of intermediate compound 3, yield: 50%. MS(M + ):554.18, 552.23; 1 HNMR(400MHz,CDCl 3 ), δ(ppm): 10.02(s, 1H), 8.01(s, 1H), 7.19(s, 1H), 3.99 - 3.92(m, 4H), 1.86 - 1.83(m, 2H), 1.55 - 1.51(m, 4H), 1.26 - 1.21(m, 12H), 0.93 - 0.83(m, 12H). The synthetic route is as follows:

[0059]

[0060] 4) Weigh 1.38 molar equivalents of intermediate compound 3, 0.55 molar equivalents of compound 4, 0.07 molar equivalents of Pd(PPh 3 ) 2 Cl 2 and 0.72 molar equivalents of K 2 CO 3 Put them into a three-necked round-bottom flask. After evacuating, add 15 molar equivalents of deionized water and 60 molar equivalents of toluene. Reflux under condensation at 80 °C for 2 hours, then raise the temperature to 90 °C and react for 15 hours before stopping the reaction. Extract with ethyl acetate and dry with anhydrous magnesium sulfate. Use petroleum ether and dichloromethane as eluents and purify by column chromatography to obtain 0.48 molar equivalents of intermediate compound 5, with a yield of 34.78%; MALD-TOF (M+): 2109.21; 1HNMR (400 MHz, CDCl3), δ (ppm): 9.99 (s, 2H), 8.03 (s, 2H), 7.99 (s, 2H), 7.51 (s, 2H), 7.25 (s, 2H), 4.03 - 3.99 (m, 4H), 3.96 - 3.93 (m, 4H), 1.75 - 1.68 (m, 12H), 1.52 - 1.50 (m, 8H), 1.25 - 1.20 (m, 136H), 0.95 - 0.74 (m, 36H). The synthetic route is as follows:

[0061]

[0062] 5) Weigh 1.2 molar equivalents of intermediate compound 5 and 3 molar equivalents of compound 6 and put them into a three-necked round-bottom flask. After cooling to -1 °C under an argon atmosphere, add 200 molar equivalents of chloroform and 5 molar equivalents of pyridine and react for 12 hours. After the reaction is completed, wash and filter with methanol. Use petroleum ether and dichloromethane as eluents and purify by column chromatography to obtain 0.8 molar equivalents of the A-D-A type indacenodithiophene planar conjugated derivative, with a yield of 66.67%. MALD-TOF (M + ):2474.17; 1 HNMR(400MHz,CDCl 3 ),δ(ppm):8.98(s,2H),8.49(s,2H),8.38(s,2H),8.02(s,2H),7.55(s,2H),7.39(s,2H),7.23(s,2H),4.35 - 4.29(m,8H),2.41 - 0.85(m,192H); 13 CNMR(100MHz,CDCl 3), δ(ppm): 191.3, 182.1, 148.2, 145.7, 144.4, 143.9, 142.2, 138.5, 137.2, 136.9, 135.5, 134.2, 133.9, 130.3, 127.5, 122.7, 120.5, 116.8, 111.4, 110.9, 94.8, 72.9, 71.4, 55.6, 46.4, 41.5, 32.3 31.8, 31.4, 30.9, 29.9, 24.5, 24.2, 23.9, 23.7, 15.3, 12.1; Elemental analysis: Anal. calcd for C 154 H 214 N 4 O 6 S 8 : C, 74.77; H, 8.72; N, 2.26; Found: C, 74.72; H, 8.77; N, 2.28. The synthetic route is as follows:

[0063]

[0064] The UV-visible absorption spectrum of the A-D-A type indacenodithiophene planar conjugated derivative is as Figure 1 shown; The top view of the molecular optimal conformation calculated by DFT (B3LYP / 6-311G(d,p)) is as Figure 2 shown, and the side view is as Figure 3 shown.

[0065] Example 2

[0066] Preparation of Organic Solar Cells

[0067] The ITO glass was ultrasonically cleaned in deionized water, ethanol, and isopropanol for 20 minutes in sequence, and then dried at 80 °C for 8 hours. After being treated in an ultraviolet ozone cleaner for 20 minutes, a 30-nm-thick PEDOT:PSS was spin-coated as the anode modification layer and dried at 150 °C for 10 minutes for standby. 7.27 mg of PM6 and 8.73 mg of Y6 were weighed respectively as the active layer materials, with a total weight of 16 mg. The A-D-A type indacenodithiophene planar conjugated derivative (IDT-BDT-IC) in Example 1 was mixed with the active layer materials at a weight ratio of 0 to 1:100. 1 mL of chloroform was added and stirred to dissolve to form an active layer additive blend solution. The solution was spin-coated on the PEDOT:PSS anode modification layer to form a 100-nm-thick active layer, and annealed at 110 °C for 5 minutes. Acetic acid was added to the PDIN methanol solution at a volume ratio of 0.5:100, and the PDIN solution was spin-coated on the active layer to form a 10-nm-thick PDIN as the cathode modification layer. Finally, a silver electrode with a thickness of about 100 nm was vacuum-evaporated to complete the preparation of the organic solar cell, and the effective area of the cell was 4 mm 2 , and the structure of the prepared solar cell is as Figure 4 shown.

[0068] Performance testing of organic solar cells

[0069] The external quantum efficiency was tested by OPS-A500, and the external quantum efficiency of the prepared solar cell is as Figure 5 shown; under the simulated solar light source of AM1.5, the J-V curve test was carried out at a light intensity of 100 mW / cm 2 . The measured solar device parameters are shown in Table 1, and the J-V curve of the prepared solar cell is as Figure 6 shown.

[0070] Table 1 Device parameters of PM6:Y6 organic solar cells at different additive concentrations

[0071]

[0072] As Figure 1As shown, the A-D-A type indacenodithiophene planar conjugated derivative (IDT-BDT-IC) in Example 1 exhibits two distinct characteristic absorption peaks in the ranges of 400 - 500 nm and 600 - 750 nm. It shows complementary absorption characteristics with traditional active layers such as PM6:Y6 and D18:Y6, which can assist the active layer in absorbing more sunlight, thereby obtaining a high short-circuit current and photoelectric conversion efficiency. Therefore, adding the A-D-A type indacenodithiophene planar conjugated derivative (IDT-BDT-IC) in Example 1 into the active layer can effectively improve the optoelectronic performance of the active layer. As Figure 5 shown, adding 0.25 wt% of IDT-BDT-IC can improve the external quantum efficiency in the wavelength ranges of 330 - 360 nm and 630 - 700 nm of the active layer, thereby effectively improving the photoelectric conversion efficiency of the battery. As shown in Table 1, by adding 0.25 wt% of IDT-BDT-IC, the short-circuit current of the battery increases from 26.3 mA / cm 2 to 27.0 mA / cm 2 , the efficiency of the battery increases from 15.81% to 16.45%, and the J-V characteristics of the battery ( Figure 6 ) are significantly improved.

[0073] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. An A-D-A type indacenodithiophene planar conjugated derivative, characterized in that, the structural formula of the A-D-A type indacenodithiophene planar conjugated derivative is: Among them, R 1 is selected from straight-chain or branched-chain alkyl groups having 1 to 20 carbon atoms; R 2 , R 3 are each independently selected from straight-chain or branched-chain alkyl groups having 1 to 6 carbon atoms.

2. The A-D-A type indacenodithiophene planar conjugated derivative according to claim 1, characterized in that, R 1 a straight-chain or branched alkyl group selected from C16; R 2 and R 3 are straight-chain or branched alkyl groups selected from C2 or C4.

3. A preparation method of the A-D-A type indacenodithiophene planar conjugated derivative according to claim 1 or 2, characterized in that, comprises the following steps: S1. Under an inert atmosphere, react benzothieno[3,2-b]benzothiophene-4,8-dione with compound A to obtain compound B S2. Under an inert atmosphere, subject compound B obtained in step S1 to a substitution reaction with N-bromosuccinimide to obtain compound C S3. Under an inert atmosphere, compound C obtained in step S2 undergoes a Vilsmeier-Haack reaction under the action of N,N-dimethylformamide and phosphorus oxychloride to form compound D S4. Combine the compound D obtained in step S3 with compound E Perform a Suzuki coupling reaction under the catalysis of a palladium catalyst to obtain compound F S5. Combine the compound F obtained in step S4 with the compound G to undergo a Knoevenagel condensation reaction to obtain an A-D-A type indacenodithiophene planar conjugated derivative; The reaction temperature of step S2 is 0 to 5 °C.

4. The preparation method of the A-D-A type indacenodithiophene planar conjugated derivative according to claim 3, characterized in that, The molar ratio of benzo[1,2-b:4,5-b']dithiophene-4,8-dione to compound A in step S1 is 1:2 to 3.

5. The preparation method of the A-D-A type indacenodithiophene planar conjugated derivative according to claim 3, characterized in that, The molar ratio of compound B to N-bromosuccinimide in step S2 is 1:0.9 to 1.

1.

6. The preparation method of the A-D-A type indacenodithiophene planar conjugated derivative according to claim 3, characterized in that, The molar ratio of compound D to compound E in step S4 is 2 to 3:

1.

7. The preparation method of the A-D-A type indacenodithiophene planar conjugated derivative according to claim 3, characterized in that, The molar ratio of compound F to compound G in step S5 is 2 to 3:

1.

8. An application of the A-D-A type indacenodithiophene planar conjugated derivative according to claim 1 or 2, characterized in that, it is used for preparing the active layer of an organic solar cell or as a material for the active layer of an organic solar cell.

9. An organic solar cell, characterized in that, the battery device comprises an active layer; the active layer is made of the A-D-A type indacenodithiophene planar conjugated derivative according to claim 1 or 2 or is prepared from the A-D-A type indacenodithiophene planar conjugated derivative as a material.

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