Benzodithiophene diketone dimer as well as preparation method and application thereof

Abstract

The invention discloses a benzodithiophene diketone dimer as well as a preparation method and application thereof, and belongs to the technical field of organic photoelectric devices. The structural formula of the benzodithiophene diketone dimer is as shown in the specification. According to the invention, the dimer is synthesized from a simple non-fullerene receptor containing benzodithiophene diketone through a linker unit. The dimer is simple and convenient to synthesize, adjustable in structure, extremely high in green synthesis degree and high in thermal stability, and the stability of a device can be effectively improved. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to the technical field of organic optoelectronic devices, and more specifically, to a benzodithiophene dione-based dimer, a preparation method thereof, and an application thereof. Background Art

[0002] Organic solar cells benefit mankind by converting clean solar energy into electrical energy required for modern life. Compared with inorganic solar cells, they have attracted much attention because of their low production cost, simple process, good flexibility, and the ability to prepare photovoltaic products on a large scale. With the continuous optimization and improvement of the photovoltaic material system and device structure, the application of high-performance non-fullerene acceptors has not only refreshed the efficiency record of organic photovoltaic devices, narrowed the gap with crystalline silicon cells, but also increased the possibility of commercialization of organic solar cells.

[0003] The active layer of an organic solar cell includes a donor material and an acceptor material. Currently, classic polymer donor materials include polymers such as D18 and PM6. Among them, the chemical structure of PM6 includes a benzodithiophene unit and a benzodithiophene dione unit. From a chemical structure perspective, if the acceptor material also uses polymer donor-related units, it may be possible to achieve additional intermolecular interactions, enhance the morphological stability of the active layer, and improve the device lifetime. Moreover, studies on Y-series polymers have shown that the preparation and application of polymers are beneficial to improving device stability. However, existing dimer acceptor materials are all single molecules with polycyclic fused rings, which have a large synthesis complexity and cost constraints. To overcome the imbalance between material cost and device performance, dimers based on simple fused-ring molecules have great potential.

[0004] CN 115850300 A discloses a small molecule acceptor based on two-dimensional side-chain substituted benzodithiophene dione. This acceptor is mainly a single molecule, and the solar cell prepared as the active layer has good device stability, but its device stability can be further improved. Summary of the Invention

[0005] In order to solve the problems existing in the above-mentioned prior art, an object of the present invention is to provide a benzodithiophene dione-based dimer.

[0006] Another object of the present invention is to provide a preparation method of a benzodithiophene dione-based dimer.

[0007] Another object of the present invention is to provide the application of the above-mentioned benzodithiophene dione-based dimer in the preparation of solar cells.

[0008] Another object of the present invention is to provide a solar cell.

[0009] In order to achieve the above objects, the present invention provides the following technical solutions:

[0010] A benzodithiophene dione dimer has the following chemical structural formula:

[0011]

[0012] Wherein, RL is a linker unit, Ar is a bridging unit, IC is an end group unit, and R is a side chain;

[0013] RL is selected from alkyl groups having C1 to C 12 , alkylthio groups having C1 to C 12 , and alkoxy groups having C1 to C 12 ; Ar is selected from aromatic rings; IC is selected from electron-deficient units; R is selected from alkyl groups having C1 to C 12 or hydrogen.

[0014] Specifically, the RL is an alkyl group having C1 to C 12 .

[0015] Preferably, the RL is an alkyl group having C6 to C8.

[0016] Specifically, the Ar is one of phenyl, thiophenyl, selenophenyl, furyl, thienothiophenyl, dithienocyclopentadienyl, dithienopyrrolyl, dithienothiophenylene, thienothiadiazolyl; the above groups may be substituted by 1 to 4 substituents, and the substituents are selected from halogens, alkyl groups having C1 to C 24 or alkoxy groups.

[0017] Specifically, the Ar is one of thiophenyl, thienothiophenyl, dithienocyclopentadienyl; the above groups may be substituted by 1 to 4 substituents, and the substituents are selected from halogens, alkyl groups having C1 to C 24 or alkoxy groups.

[0018] Preferably, the Ar is dithienocyclopentadienyl, and the group may be substituted by 2 substituents, and the substituents are 2-ethylhexyl.

[0019] Specifically, the IC is formed from any one of the following precursors:

[0020]

[0021] Wherein, R4 is selected from H, F, Cl, Br, I, CH3O, CH3.

[0022] Preferably, the precursor of the IC is dicyanoindanone and its halogenated derivatives.

[0023] Specifically, the R is an alkyl group having C4 to C 10 .

[0024] Preferably, the R is 2-ethylhexyl.

[0025] A preparation method of the above-mentioned benzodithiophene dione dimer, wherein the dimer is prepared by reacting a first intermediate with an IC precursor, and the first intermediate has the following chemical structural formula:

[0026]

[0027] Wherein, RL is a linker unit, Ar is a bridging unit, and R is a side chain;

[0028] RL is selected from alkyl groups of C1-C 12 , alkylthio groups of C1-C 12 and alkoxy groups of C1-C 12 ; Ar is selected from aromatic rings; R is selected from alkyl groups of C1-C 12 or hydrogen.

[0029] Specifically, the dimer is prepared by reacting the first intermediate with the IC precursor through the Knoevenagel reaction.

[0030] Specifically, the synthetic route of the first intermediate is as follows:

[0031]

[0032] Wherein, RL is a linker unit, Ar is a bridging unit, and R is a side chain;

[0033] RL is selected from alkyl groups of C1-C 12 alkylthio groups of C1-C 12 and alkoxy groups of C1-C 12 ; Ar is selected from aromatic rings; R is selected from alkyl groups of C1-C 12 or hydrogen.

[0034] The present invention also protects the application of the above dimer or the dimer prepared by the above preparation method in the preparation of solar cells.

[0035] A solar cell using the above dimer as an active layer.

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

[0037] The present invention synthesizes a dimer of a simple non-fullerene acceptor containing benzodithiophene dione through a linker unit. The dimer is simple to synthesize, has adjustable structure, and has a very high degree of green synthesis. In addition, the provided dimer has high thermal stability and can effectively improve the device stability.

[0038] The solar cell prepared by using the benzodithiophene dione dimer as an active layer in the present invention has good device stability. Description of the Drawings

[0039] Figure 1 Absorption graphs of the solution and thin film of Example 1.

[0040] Figure 2 Thermogravimetric graphs of Examples 1 and 2.

[0041] Figure 3 Electrochemical curve graph of Example 1.

[0042] Figure 4 Device efficiency thermal stability curve graph of the organic solar cell in Example 4.

[0043] Figure 5 J-V curve graph of the organic solar cell in Example 5.

[0044] Figure 6 Device thermal stability curve graph of the organic solar cell in Example 5.

[0045] Figure 7 T80 lifetime fitting curve graph of the thermal stability of the organic solar cell in Example 5.

[0046] Figure 8 Device thermal stability curve graph of the organic solar cell in Example 6. Detailed implementation manners

[0047] The present invention will be further described below in conjunction with examples. These examples are only used to illustrate the present invention and not to limit the scope of the present invention. For the experimental methods without specific conditions in the following examples, they are generally carried out according to the conventional conditions in the art or according to the conditions recommended by the manufacturer; the raw materials, reagents, etc. used, unless otherwise specified, are all raw materials and reagents that can be obtained from commercial channels such as conventional markets. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection required by the present invention.

[0048] Example 1

[0049] This example provides a benzodithiophene dione dimer (2BDD-C6-8F), and its preparation process is as follows:

[0050] (1) Preparation of 1,6-bis(ethylhexylthienyl)hexane (EH-T-C6-EH), the reaction formula is as follows:

[0051]

[0052] 50 mmol of thiophene-2-EH was added to a 250 ml two-necked flask, 50 ml of ultra-dry tetrahydrofuran was added, N2 was passed through for 10 min, and 21 ml of n-butyllithium was slowly added dropwise under a -78 °C reaction bath and stirred for 1 h. Subsequently, it was transferred to a 50 °C oil bath and heated for 1 h, and then returned to the -78 °C reaction bath. 20 mmol of 1,6-dibromohexane was slowly added dropwise and stirred at low temperature for 30 min, and then heated and reacted overnight in a 50 °C oil bath. After the reaction was completed, water was added to quench the reaction, extracted 3-4 times with petroleum ether, dried over anhydrous sodium sulfate, the solvent was removed, and purified by silica gel column chromatography using petroleum ether as the eluent to obtain 9.24 g of the product (97%). 1 1H NMR (400 MHz, CDCl3), δ (ppm): 6.53 (q, J = 3.4 Hz, 4H), 2.76 - 2.65 (m, 8H), 1.64 (p, J = 7.1 Hz, 4H), 1.54 (d, J = 8.0 Hz, 2H), 1.43 (s, 2H), 1.30 (dd, J = 18.3, 5.1 Hz, 16H), 0.92 - 0.84 (m, 12H).

[0053] (2) Preparation of EH-BDD-C6-BDD-EH, the reaction formula is as follows:

[0054]

[0055] 15 mmol of 2,5-dibromo-3,4-dicarboxythiophene was added to a 100 mL two-necked flask, 40 ml of ultra-dry dichloromethane was added, N2 was passed through, and one drop of ultra-dry N,N-dimethylformamide was added. Subsequently, 10 ml of oxalyl chloride was slowly added dropwise and reacted for 12 h. After the reaction was completed, the solvent was removed and the next reaction was carried out without purification. This reaction yielded 2,5-dibromo-3,4-diformylchlorothiophene.

[0056] An EH-T-C6-T-EH solution dissolved in a 50 ml solvent with a 1:1 ratio of ultra-dry dichloromethane and 1,2-dichloroethane was added to a 250 ml two-necked flask, and a solution of 2,5-dibromo-3,4-diformylchlorothiophene dissolved in 50 ml of the same ultra-dry mixed solvent was added. N2 was passed through and stirred in an ice bath for 20 min. Subsequently, 96 mmol of AlCl3 powder was added in portions in the ice bath, and then stirred in the ice bath for 30 min and allowed to react at room temperature for 5 h. After the reaction was completed, the reaction solution was poured into 0.1 mol / L ice HCl solution to quench the reaction, extracted 3-4 times with dichloromethane, dried over anhydrous sodium sulfate, and after removing the solvent, purified by silica gel column chromatography using dichloromethane / petroleum ether (2:1) as the eluent. Subsequently, recrystallized with dichloromethane and petroleum ether to obtain a pale yellow solid (5 mmol, 33%). 1HNMR (400 MHz, CDCl3), δ (ppm): 3.37 - 3.25 (m, 8H), 1.76 (q, J = 6.8, 6.0 Hz, 6H), 1.51 (p, J = 3.4 Hz, 8H), 1.45 - 1.23 (m, 12H), 0.89 (dt, J = 8.9, 6.9 Hz, 12H).

[0057] (3) Preparation of the first intermediate, the reaction formula is as follows:

[0058]

[0059] Add 1.2 mmol of EH-BDD-C6-BDD-EH, 5.4 mmol of DTC-CHO, 9.6 mmol of cesium carbonate, 0.12 ml of pivalic acid, and 30 ml of ultra-dry o-xylene into a 50 ml two-necked flask. Pass N2 and stir for 20 min, then add 0.12 mmol of Pd2(dba)3 and 0.24 mmol of P(o-CH3OPh)3, and heat up to 120 °C for overnight reaction. After the reaction is completed, quench the reaction with water, extract with dichloromethane 3 - 4 times, dry with anhydrous sodium sulfate, remove the solvent, and purify by silica gel column chromatography using petroleum ether / dichloromethane (1:1) as the eluent. Finally, recrystallize with methanol to obtain a dark red solid (0.63 mmol, 53%).

[0060] 1 H NMR (400 MHz, CDCl3), δ (ppm): 9.87 (d, J = 4.0 Hz, 4H), 7.74 - 7.66 (m, 4H), 7.60 (q, J = 3.3 Hz, 4H), 3.44 (t, J = 7.6 Hz, 4H), 3.34 (ddd, J = 23.9, 12.3, 6.9 Hz, 4H), 1.97 (dd, J = 13.3, 7.8 Hz, 16H), 1.81 (dt, J = 18.0, 6.6 Hz, 6H), 1.57 (s, 8H), 0.97 (ddd, J = 24.8, 12.8, 6.6 Hz, 84H), 0.81 - 0.58 (m, 60H).

[0061] (4) Preparation of the dimer 2BDD-C6-8F, the reaction formula is as follows:

[0062]

[0063] Add 0.06 mmol of 2BDD-C6-4DTC-4CHO, 0.3 mmol of IC(2F), and 25 ml of chloroform into a 50 ml two-necked flask. Pass N2 and stir for 20 min. Then, add 0.1 ml of pyridine dropwise and heat under reflux at 60 °C overnight. After the reaction is completed, drop the reaction solution into methanol for recrystallization, filter, and purify by silica gel column chromatography using petroleum ether / dichloromethane (1:2) as the eluent. Finally, recrystallize twice with methanol to obtain the dimer 2BDD-C6-8F (0.033 mmol, 55%). 1 1H NMR (400 MHz, CDCl3), δ (ppm): 8.93 - 8.87 (m, 4H), 8.57 - 8.48 (m, 4H), 7.71 (dddt, J = 25.2, 18.3, 13.2, 5.8 Hz, 12H), 3.47 (s, 4H), 3.38 (d, J = 6.1 Hz, 4H), 2.02 (s, 22H), 1.85 (d, J = 30.8 Hz, 8H), 1.08 - 0.90 (m, 84H), 0.79 - 0.62 (m, 60H).

[0064] The absorption test was carried out on the dimer prepared in Example 1, and the test results are as Figure 1 shown. It can be seen from Figure 1 that the maximum absorption peaks of the solution and film of the dimer prepared in Example 1 are 689 nm and 771 nm, respectively.

[0065] The electrochemical test was carried out on the dimer prepared in Example 1, and the test results are as Figure 3 shown. According to the electrochemical test results, the calculated electrochemical energy levels HOMO and LUMO of the dimer are -5.57 eV and -3.88 eV, respectively.

[0066] Example 2

[0067] This example provides a benzodithiophene dione dimer (2BDD-C6-4F), which is prepared by the Knoevenagel reaction of the first intermediate and monofluoro dicyanoindanone. The specific preparation method is the same as that in (4) of Example 1, except that the difluoro dicyanoindanone (i.e., IC(2F)) is replaced by monofluoro dicyanoindanone. The reaction formula is as follows:

[0068]

[0069] The thermogravimetric analysis test was carried out on Example 1 and Example 2, and the test results are as Figure 2 shown. It can be seen from Figure 2 that the benzodithiophene dione dimers prepared in Example 1 and Example 2 maintain their mass below 339 °C, indicating that the prepared dimers have good thermal stability.

[0070] Example 3

[0071] This example provides a benzodithiophene dione dimer (EHBDD-C8-8F), and its preparation method is the same as that of Example 1, except that 1,6-dibromohexane in Example 1(1) is replaced by 1,8-dibromooctane. The preparation route is as follows:

[0072]

[0073] Example 4

[0074] Application of EHBDD-C8-8F in an organic photovoltaic device based on donor PM6

[0075] Preparation process of an organic photovoltaic device using PM6 polymer as the donor material and EHBDD-C8-8F as the non-fullerene acceptor material: The structure of an organic photovoltaic cell device with ITO as the anode is: ITO / PEDOT:PSS / polymer donor PM6:dimer prepared in Example 3 = 1:1.2 / PDINN / Ag. The device fabrication process is as follows: Using a pre-cleaned ITO glass as the anode, PEDOT:PSS is spin-coated on the ITO substrate by spin coating, with a rotation speed of 3000 rpm and a time of 30 s. Anneal at 150 °C for 12 min in an air atmosphere to form a dense anode interfacial layer film. Then spin coat a photovoltaic active layer (PM6 and EHBDD-C8-8F dimer) with a thickness of about 110 nm. Anneal at 120 °C for 10 minutes. After cooling, spin coat a 1.5 mg / mL PDINN methanol solution on the active layer at a rotation speed of 3000 rpm for 30 s, without annealing. After the solvent naturally evaporates, a Ag electrode with a thickness of about 100 nm is deposited by high vacuum thermal evaporation, and the organic solar cell is obtained.

[0076] The device stability is studied at 80 °C under a nitrogen atmosphere, and the corresponding device stability test is as Figure 4 shown. After thermal annealing for 248 hours, the device still maintains 89.4% of the original efficiency. More remarkably, when the annealing time is 700 hours, the device efficiency can still maintain 88.9% of the original efficiency. According to the linear extrapolation method, the T80 life of the device based on EHBDD-C8-8F exceeds 15000 hours.

[0077] Example 5

[0078] Preparation of a ternary device based on EHBDD-C8-8F

[0079] The preparation process of an organic photovoltaic device using D18 polymer as the donor material, L8-BO acceptor as the non-fullerene acceptor material, and EHBDD-C8-8F dimer as the third component: It is equivalent to the preparation process of Example 4, and the only difference is that the active layer material is replaced with a ternary blend of D18:L8-BO:EHBDD-C8-8F. A bias voltage is applied between the ITO and Ag electrodes, and its cell characteristics are measured under illumination of AM 1.5 simulated sunlight at 100 mW / cm². Without any additives, the open-circuit voltage of the as-cast cell device based on D18:L8-BO is 0.918 V, the short-circuit current is 24.82 mA / cm², the fill factor is 75.96%, and the energy conversion efficiency is 17.32%. While the energy conversion efficiency of the as-cast device obtained by adding 10% by mass of the EHBDD-C8-8F dimer is increased to 18.12%, the corresponding open-circuit voltage is 0.884 V, the short-circuit current is 25.96 mA / cm², and the fill factor is 78.91%. The corresponding device current and voltage curves are shown in Figure 5 , and the specific parameter comparison is shown in Table 1 as follows:

[0080] Table 1

[0081] Active layer (without additives) <![CDATA[V oc (V)]]> <![CDATA[J sc (mA / cm 2 )]]> FF (%) PCE (%) D18:L8-BO 0.918 24.82 75.96 17.32 D18:L8-BO:EHBDD-C8-8F 0.884 25.96 78.91 18.12

[0082] The device stability was studied at a high temperature of 80 °C and in a nitrogen atmosphere. The corresponding device stability test is shown in Figure 6 . After thermal annealing for 167 hours, the device still maintained 84.3% of its original efficiency. More remarkably, when the annealing time was 700 hours, the device efficiency could still maintain 85.1% of its original efficiency. According to the above linear extrapolation method, as shown in Figure 7 , the T80 lifetime of the ternary device based on EHBDD-C8-8F exceeded 15,000 hours.

[0083] Example 6

[0084] Application of 2BDD-C6-8F in an organic photovoltaic device based on the donor PM6

[0085] Preparation process of an organic photovoltaic device using PM6 polymer as the donor material and 2BDD-C6-8F as the non-fullerene acceptor material: The structure of the organic photovoltaic cell device with ITO as the anode is: ITO / PEDOT:PSS / polymer donor PM6: dimer prepared in Example 1 = 1:1.2 / PDINN / Ag. The device fabrication process is as follows: Using pre-cleaned ITO glass as the anode, PEDOT:PSS is spin-coated on the ITO substrate at a rotation speed of 3000 rpm for 30 s. Anneal at 150 °C for 12 min in an air atmosphere to form a dense anode interfacial layer film. Then spin-coat a photovoltaic active layer (PM6 and 2BDD-C6-8F dimer) with a thickness of about 110 nm. Anneal at 120 °C for 10 minutes. After cooling, spin-coat a 1.5 mg / mL PDINN methanol solution on the active layer at a rotation speed of 3000 rpm for 30 s without annealing. After the solvent naturally evaporates, deposit an Ag electrode with a thickness of about 100 nm by high-vacuum thermal evaporation to obtain the organic solar cell described above.

[0086] The device stability was studied at 80 °C under a nitrogen atmosphere, and the corresponding device stability test is as Figure 8 shown. More remarkably, when the annealing time is 100 hours, the device efficiency can still maintain 86% of the original efficiency. According to the above linear extrapolation method, the T80 life of the device based on 2BDD-C6-8F exceeds 3000 hours.

[0087] 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. A benzodithiophene dione dimer, characterized in that, It has the following chemical structural formula: Wherein, RL is a linker unit, Ar is a bridging unit, IC is an end group unit, and R is a side chain; RL is selected from C1-C 12 alkyl, C1-C 12 alkylthio, C1-C 12 alkoxy; Ar is selected from an aromatic ring; IC is selected from an electron-deficient unit; R is selected from C1-C 12 alkyl.

2. The dimer according to claim 1, wherein The RL is an alkyl group of C1 to C 12 as described.

3. The dimer according to claim 1, wherein Ar is one of phenyl, thienyl, selenophenyl, furyl, thienothiophenyl, dithienocyclopentadienyl, dithienopyrrolyl, dithienothiophenylene, thienothiadiazolyl; the above groups may be substituted by 1 to 4 substituents, and the substituents are selected from halogen, C1-C 24 alkyl or alkoxy.

4. The dimer according to claim 1, wherein Ar is one of thienyl, thienothiophenyl, and dithienocyclopentadienyl; the above groups may be substituted by 1 to 4 substituents, and the substituents are selected from halogen, C1-C 24 alkyl or alkoxy.

5. The dimer according to claim 1, wherein The IC is formed from any one of the following precursors: Wherein, R4 is selected from H, F, Cl, Br, I, CH3O, CH3.

6. The dimer according to claim 1, wherein The precursor of the IC is dicyanoindanone and its halogenated derivatives.

7. A method for preparing the benzodithiophene dione dimer according to any one of claims 1 to 6, characterized in that, The dimer is prepared by reacting a first intermediate with an IC precursor, and the first intermediate has the following chemical structural formula: Wherein, RL is a linker unit, Ar is a bridging unit, and R is a side chain; RL is selected from C1-C 12 alkyl, C1-C 12 alkylthio, C1-C 12 alkoxy; Ar is selected from an aromatic ring; R is selected from C1-C 12 alkyl or hydrogen.

8. The preparation method according to claim 7, characterized in that, The synthesis route of the first intermediate is as follows: Wherein, RL is a linker unit, Ar is a bridging unit, and R is a side chain; RL is selected from C1-C 12 alkyl, C1-C 12 alkylthio, C1-C 12 alkoxy; Ar is selected from an aromatic ring; R is selected from C1-C 12 alkyl or hydrogen.

9. Use of the dimer according to any one of claims 1 to 6 or the dimer prepared by the preparation method according to any one of claims 7 to 8 in the preparation of a solar cell.

10. A solar cell, characterized in that, Using the dimer according to any one of claims 1 to 6 as the active layer.

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