Two-dimensional pi-bridge substituted pyrene nucleus small molecule acceptor material as well as preparation method and application thereof

Abstract

The invention discloses a two-dimensional pi-bridge substituted pyrene nucleus small molecule acceptor material as well as a preparation method and application thereof, and relates to the field of organic solar cell materials. The structural general formula of the acceptor material is shown in the specification, wherein Ar1 and Ar2 are independent aromatic groups. The micromolecule acceptor material provided by the invention takes a pyrene derivative as a core and has a non-fused asymmetric chemical structure, and compared with an existing micromolecule acceptor material with a common pyrene core, the micromolecule acceptor material provided by the invention has a two-dimensional pi-bridge structure and has the advantages that the mobility is remarkably improved, the absorption spectrum is remarkably subjected to red shift and the like; the utilization rate of sunlight is improved; the light current of the organic solar cell can be obviously improved; the material has the advantage of high energy conversion efficiency when applied to solar cells.

Description

Technical Field

[0001] This invention relates to the field of organic solar cells, and in particular to a two-dimensional π-bridged substituted pyrene nucleus small molecule acceptor material and its preparation method. Background Technology

[0002] Organic solar cells can directly convert solar energy into electrical energy and have attracted widespread attention due to their advantages such as light weight, solution-processability, and low cost. Acceptor materials, as one of the core components of organic solar cells, have become a key research focus for scientists. Non-fullerene acceptors (NFAs) are gradually emerging as a leading acceptor material due to their unique advantages, including easily modifiable molecular structures, large adjustable optical band gaps, extended light absorption edges into the near-infrared region, strong energy level tunability, high open-circuit voltage, and easily tunable molecular planarity and crystallinity. Small molecule non-fullerene acceptor materials (SMAs) possess well-defined molecular structures, better batch-to-batch reproducibility, high purity, and easily tunable absorption spectra and chemical energy levels, making them one of the current research hotspots. To date, the power conversion efficiency (PCE) of organic solar cells based on small molecule acceptor materials has exceeded 20%.

[0003] Small molecule acceptor materials generally employ fused-ring structures, making their synthesis complex and involving lengthy synthetic routes that result in low overall yields, significantly increasing synthesis costs and hindering commercial applications. Compared to fused-ring small molecule acceptors, non-fused small molecule acceptors are relatively simple to synthesize, but their current availability is limited by their limited variety and slightly lower efficiency. Therefore, developing novel and highly efficient non-fused-ring small molecule acceptors is crucial. Pyrene is an inexpensive and readily available fused-ring aromatic hydrocarbon composed of four fused benzene rings. Its planar molecular structure and excellent electron delocalization capabilities give pyrene and its derivatives strong π-π packing, good crystallinity, and high carrier mobility. Consequently, pyrene compounds are widely used in organic electronics and other fields. However, research on pyrene-based small molecule acceptors is still relatively limited. To achieve this goal, it is urgent to provide a non-fused pyrene derivative core small molecule acceptor material that broadens the absorption spectrum, improves photocurrent and energy conversion efficiency, while reducing costs to address the shortcomings of existing technologies.

[0004] While current highly efficient non-fullerene receptors such as Y6 (J. Am. Chem. Soc. 2020, 142, 14532) have efficiencies exceeding 18%, their synthesis requires more than eight steps, resulting in high costs. In contrast, non-fused receptors (Chem. Mater. 2021, 33, 3946) reduce the number of steps to five, but their efficiencies are generally <5%. Summary of the Invention

[0005] The purpose of this invention is to provide a two-dimensional π-bridged substituted pyrene nucleus small molecule acceptor material and its preparation method.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A two-dimensional π-bridge-substituted pyrene nucleus small molecule acceptor material, with the following general structural formula:

[0008]

[0009] In general formula (I), Ar 1 It is one of the following structural units:

[0010] R 1 C1-C 20 Alkyl groups;

[0011] Ar 2 It is one of the following structural units:

[0012]

[0013] Another object of the present invention is to provide a method for preparing the two-dimensional π-bridge-substituted pyrene nucleus small molecule acceptor material, comprising the following steps:

[0014] Step 1: 3,10-dibromo-1,9-diisopropylpyrene (a) is coupled with a compound of general formula (III) via Stille coupling reaction to give a compound of general formula (b);

[0015]

[0016] Step 2: The compound of general formula (b) is reacted with phosphorus oxychloride in an organic solvent to formylate the compound of general formula (c).

[0017]

[0018] Step 3: The compound of general formula (c) is subjected to a Knauven-Gail condensation reaction with the compound of general formula (IV) to obtain the compound of general formula (I).

[0019]

[0020] Therefore, this invention provides a two-dimensional π-bridged pyrene nucleus small molecule acceptor material. Compared with existing fused-ring small molecule acceptor materials (such as ITIC and Y6), the synthesis cost of this non-fused small molecule acceptor material is significantly reduced. Thus, the two-dimensional π-bridged pyrene nucleus small molecule acceptor material of this invention, when applied to organic solar cells, can simultaneously achieve high energy conversion efficiency and significantly reduced synthesis cost, which is beneficial for commercial application.

[0021] Preferably, in step one, under a protective atmosphere, 3,10-dibromo-1,9-diisopropylpyrene (a) and the compound of general formula (III) and toluene are placed in a reactor, and tetra(triphenylphosphine)palladium is added. The mixture is refluxed, cooled, poured into water, extracted with dichloromethane, the solvent is removed by rotary evaporation, and purified by column chromatography to obtain the compound of general formula (b).

[0022] More preferably, the toluene is purified toluene.

[0023] Preferably, in step two, under an argon atmosphere, the compound of general formula (b), 1,2-dichloroethane and DMF are placed into a reactor, phosphorus oxychloride is added under an ice-water bath, the mixture is stirred, refluxed, cooled and then an aqueous solution is added, followed by extraction with dichloromethane, solvent removal by rotary evaporation, and purification by column chromatography to obtain the compound having general formula (c).

[0024] More preferably, the mixture is stirred at room temperature for 0.5 h before reflux reaction.

[0025] Preferably, in step five: the compound of general formula (c), the compound of general formula (IV) and chloroform are added to the reactor in sequence, pyridine is added under nitrogen protection, the mixture is heated to reflux, cooled and precipitated with methanol, and purified by column chromatography to obtain the compound of general formula (II).

[0026] More preferably, the reflux time is 24 hours.

[0027] Another object of the present invention is to provide a two-dimensional π-bridged pyrene nucleus small molecule acceptor material having the chemical structure of general formula (II):

[0028]

[0029] The preparation method of the above-mentioned two-dimensional π-bridge-substituted pyrene nucleus small molecule acceptor material (II) includes the following steps:

[0030] Step 1: Compound 1, 4-(3-(2-octyldodecyloxy)phenyl)-2-tributyltin-thiophene, and toluene were added to the reactor. Tetra(triphenylphosphine)palladium was added under argon protection. The mixture was refluxed for 24 hours. After cooling, the mixture was poured into water, extracted with dichloromethane, the solvent was removed by rotary evaporation, and purified by column chromatography to obtain compound 2.

[0031]

[0032] Step 2: Compound 2, 1,2-dichloroethane and DMF were added to the reactor under argon protection. Phosphorus oxychloride was added dropwise at 0°C. After stirring at room temperature for 0.5 h, the mixture was refluxed for 24 h. After cooling, water was added, and the mixture was extracted with dichloromethane. The solvent was removed by rotary evaporation, and the mixture was purified by column chromatography to obtain compound 3.

[0033]

[0034] Step 3: Compounds 3, 5,6-difluoro-3-(dicyanomethylene)indone and chloroform were added to the reactor in sequence. Pyridine was added under nitrogen protection, and the mixture was heated to reflux for 20 h. After cooling, the mixture was precipitated with methanol and purified by column chromatography to obtain compound (II).

[0035]

[0036] Another object of the present invention is to provide an application of the above-mentioned two-dimensional π-bridge-substituted pyrene nucleus small molecule acceptor material in organic solar cells.

[0037] The beneficial effects of this invention are:

[0038] This invention provides a two-dimensional π-bridged pyrene nucleus small molecule receptor material, its preparation method, and its application. The general structural formula of the receptor material of this invention is:

[0039] Among them, Ar 1 and Ar 2 It is an independent aromatic group. Compared with the prior art, the present invention has the following characteristics:

[0040] 1. It possesses a pyrene nucleus molecular structure, resulting in strong intermolecular interactions;

[0041] 2. It has a non-fused molecular structure, making its synthesis relatively simple and efficient, and its synthesis cost low;

[0042] 3. Two-dimensional π-bridge substitution can further enhance intermolecular interactions, broaden the absorption spectrum, and improve the utilization rate of sunlight by organic solar cells;

[0043] 4. The short-circuit current of organic solar cells is significantly improved;

[0044] 5. Organic solar cells can achieve high energy conversion efficiency.

[0045] 6. Two-dimensional π-bridges enhance intermolecular π-π stacking, redshifting the film absorption edge to the near-infrared region (622nm), and increasing carrier mobility to 10⁻³ cm⁻¹. 2 On the order of V-1s-1. Attached Figure Description

[0046] The invention will be further illustrated with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the invention.

[0047] Figure 1 Chloroform dilute solutions (10) of the receptor materials PyB-2H and PyB-2F prepared in Examples 1 and 2 - 5 Absorption spectra in the M state and in the thin film state;

[0048] Figure 2 Cyclic voltammetry curves of the receptor materials PyB-2H and PyB-2F prepared in Examples 1 and 2, respectively.

[0049] Figure 3 JV curves are shown for organic solar cells prepared by blending acceptor materials PyB-2H and PyB-2F obtained in Examples 1 and 2 with donor material PBDB-T. Detailed Implementation

[0050] The present invention will be further described in conjunction with the following embodiments.

[0051] Example 1:

[0052] A method for preparing PyB-2H, a two-dimensional π-bridge-substituted pyrene nucleus small molecule acceptor material, is described below:

[0053]

[0054] (1) Synthesis of compound 2: 3-bromophenol (1.73 g, 10 mmol), 1-bromo-2-octyldodecane (5.86 g, 16.3 mmol), 50 mL acetone, 4.5 g potassium carbonate, and 204 mg potassium iodide were added sequentially to a 250 mL single-necked flask. The mixture was refluxed under argon protection for 24 h. After cooling to room temperature, the mixture was poured into water, extracted with dichloromethane, dried over anhydrous MgSO4, and the solvent was removed by rotary evaporation. The mixture was then subjected to silica gel column chromatography (petroleum ether as eluent) to give 1.75 g of a colorless transparent liquid (yield 31.4%). 1 HNMR(CDCl3,400MHz,δ / ppm):7.14-7.10(m,1H),7.06-7.04(m,2H),6.84-6.81(m,1 H), 3.80 (d, J = 5.6Hz, 2H), 1.77-1.72 (m, 1H), 1.43-1.26 (m, 32H), 0.90-0.86 (m, 6H).

[0055] (2) Synthesis of compound 3: Compound 2 (1.75 g, 3.9 mmol), 3-thiopheneboronic acid (998 mg, 7.8 mmol), 20 mL toluene, 20 mL potassium carbonate solution (2 M), and 20 mL ethanol were added sequentially to a 250 mL two-necked flask. Under argon protection, 25 mg of Pd(PPh3)4 was added, and the reaction was carried out at 95 °C for 30 h. After cooling to room temperature, the mixture was poured into water, extracted with dichloromethane, dried over anhydrous MgSO4, the solvent was removed by rotary evaporation, and the mixture was subjected to silica gel column chromatography (petroleum ether as eluent) to give 1.47 g of pale yellow liquid (yield 83.1%). 1HNMR (CDCl3, 400MHz, δ / ppm): 7.46-7.44 (m, 1H), 7.39-7.37 (m, 2H), 7.32-7.28 (m, 1H), 7.17 (d, J = 7.7Hz, 1H), 7.13-7 .12(m,1H),6.85-6.82(m,1H),3.88-3.86(d,J=5.7Hz,2H),1.82-1.76(m,1H),1.48-1.25(m,32H),0.89-0.86(m,6H).

[0056] (3) Synthesis of Compound 4: Compound 3 (2.63 g, 5.8 mmol) and 30 mL of tetrahydrofuran were added to a 250 mL single-necked flask. Under Ar protection, 7 mL of LDA (1 M, 7.0 mmol) was added dropwise at -78 °C. After stirring at -78 °C for 1 h, tributyltin chloride (2.48 g, 7.0 mmol) was added dropwise and stirred for 0.5 h. The mixture was then moved to room temperature and reacted for another 12 h. The solution was poured into water, extracted with dichloromethane, dried over anhydrous MgSO4, and the solvent was removed by rotary evaporation to obtain Compound 4 as a pale yellow liquid. No purification was required, and it was used directly in the next reaction.

[0057] (4) Synthesis of compound 5: Compound 4, 1,6-diisopropyl-3,8-dibromopyrene (1.16 g, 2.6 mmol), and 100 mL of toluene were added sequentially to a 250 mL two-necked flask. 100 mg of Pd(PPh3)4 was added under Ar protection, and the reaction was carried out at 115 °C for 24 h. After cooling to room temperature, the mixture was poured into water, extracted with dichloromethane, dried over anhydrous MgSO4, and the solvent was removed by rotary evaporation. The mixture was then subjected to silica gel column chromatography (petroleum ether:dichloromethane = 3:1 as eluent) to give 2.16 g of a pale yellow liquid (yield 69.2%). 1 HNMR(CDCl3,400MHz,δ / ppm):8.59(d,J=9.6Hz,2H),8.37(d,J=9.7Hz,2H),8.11(s, 2H),7.67(d,J=1.3Hz,2H),7.65(d,J=1.4Hz,2H),7.39-7.35(m,2H),7.31-7.30(m, 2H),7.27-7.26(m,2H),6.90-6.89(m,2H),4.13-4.06(m,2H),3.91(d,J=5.7Hz,4H) ,1.85-1.80(m,2H),1.56(d,J=6.5Hz,12H),1.47-1.26(m,64H),0.88-0.85(m,12H).

[0058] (5) Synthesis of Compound 6: Compound 5 (850 mg, 0.71 mmol), 55 mL of 1,2-dichloroethane, and 11 mL of N,N-dimethylformamide were added to a 100 mL two-necked flask. Under Ar protection, 1.33 mL of phosphorus oxychloride (14.2 mmol) was added at 0 °C. After stirring at 0 °C for 30 min, the mixture was heated to 85 °C and reacted for 24 h. After cooling to room temperature, the mixture was added dropwise to a saturated Na2CO3 aqueous solution, extracted with dichloromethane, dried over anhydrous MgSO4, and the solvent was removed by rotary evaporation. The mixture was then subjected to silica gel column chromatography (petroleum ether:dichloromethane = 1:1 as eluent) to give 657 mg of an orange-yellow solid (yield 74.7%). 1 HNMR (CDCl3, 400MHz, δ / ppm): 10.03 (s, 2H), 8.60 (d, J = 9.6Hz, 2H), 8.42 (d, J = 9.8 Hz,2H),8.14(s,2H),7.55(s,2H),7.47-7.43(m,2H),7.21(d,J=7.7Hz,2H),7.16 (s,2H),7.04(dd,J=8.3,2.4Hz,2H),4.13-4.06(m,2H),3.91(d,J=5.6Hz,4H),1. 84-1.79(m,2H),1.56(d,J=6.9Hz,12H),1.43-1.24(m,64H),0.88-0.84(m,12H).

[0059] (6) Synthesis of PyB-2H: Compound 6 (60 mg, 0.049 mmol), 3-(dicyanomethylene)indophenone (57 mg, 0.29 mmol), 15 mL of chloroform, and 0.5 mL of ultradry pyridine were added sequentially to a 100 mL single-necked flask. The mixture was reacted at 70 °C for 20 h under Ar protection. After cooling to room temperature, the mixture was precipitated by adding methanol dropwise, followed by silica gel column chromatography (200–300 mesh) (eluent: petroleum ether: dichloromethane = 1:2). Precipitation with methanol was repeated to give 57 mg of a blue solid (yield: 71.0%). 1H NMR (CDCl3, 400MHz, δ / ppm): 8.90 (s, 2H), 8.71-8.65 (m, 4H), 8.46 (d, J = 9.7Hz, 2H), 8. 23(s,2H),7.98-7.96(d,J=8.7Hz,2H),7.81-7.73(m,4H),7.68(s,2H),7.51-7.47(m, 2H),7.15(d,J=10.0Hz,2H),7.10-7.09(m,4H),4.15-4.08(m,2H),3.93(d,J=5.7Hz,4 H),1.84-1.80(m,2H),1.59(d,J=6.7Hz,12H),1.49-1.24(m,64H),0.87-0.84(m,12H).

[0060] Example 2:

[0061] A method for preparing PyB-2F, a two-dimensional π-bridge-substituted pyrene nucleus small molecule acceptor material, is described below:

[0062]

[0063] Synthesis of PyB-2F: In a 100 mL single-necked flask, compound 6 (64 mg, 0.052 mmol), 5,6-difluoro-3-(dicyanomethylene)indophenone (72 mg, 0.31 mmol), 15 mL of chloroform, and 0.5 mL of ultradry pyridine were added sequentially. The reaction was carried out at 70 °C for 20 h under Ar protection. After cooling to room temperature, the mixture was precipitated by adding methanol dropwise, followed by silica gel column chromatography (200–300 mesh) (eluent: petroleum ether: dichloromethane = 1:2). Precipitation with methanol was repeated to give 82 mg of a blue solid (yield: 95.4%). 1 H NMR (CDCl3, 400MHz, δ / ppm): 8.89 (s, 2H), 8.66 (d, J = 9.0Hz, 2H), 8.56-8.52 (m, 2H ),8.47(d,J=9.7Hz,2H),8.22(s,2H),7.75-7.71(m,2H),7.69(s,2H),7.52-7.47( m,2H),7.14-7.11(m,4H),7.09(s,2H),4.15-4.08(m,2H),3.92(d,J=5.6Hz,4H),1 .84-1.80(m,2H),1.59(d,J=6.7Hz,12H),1.40-1.25(m,64H),0.87-0.83(m,12H).

[0064] The UV-Vis absorption spectra of the two small molecule acceptor materials PyB-2H and PyB-2F prepared in Examples 1 and 2 are as follows: Figure 1 As shown, the maximum absorption wavelengths of PyB-2H and PyB-2F in dilute chloroform solution are 585 nm and 602 nm, respectively, with PyB-2F exhibiting a 17 nm redshift. The maximum film absorption peaks of the small molecule acceptors PyB-2H and PyB-2F are 614 nm and 622 nm, respectively, showing a significant redshift compared to their solution absorption spectra. This is mainly due to the stronger π-π packing of PyB-2F. The optical band gaps of PyB-2H and PyB-2F are 1.70 eV and 1.68 eV, respectively. Compared to PyB-2H, PyB-2F has a significantly broadened absorption spectrum, which is beneficial for obtaining higher photocurrent and energy conversion efficiency in devices.

[0065] The cyclic voltammetry curves of the two small molecule acceptor materials PyB-2H and PyB-2F prepared in Examples 1 and 2 are shown below. Figure 2 As shown, the oxidation potentials (E) of PyB-2F and PyB-2H are... ox on The values ​​are 0.98V and 0.97V, and the reduction potential (E) is... red on The values ​​are -1.03V and -0.98V. According to the empirical formula E... HOMO =-(E ox on +4.8)(eV) and E LUMO =-(E red on Calculations using +4.8 eV yielded HOMO / LUMO energy levels of -5.78 eV / -3.77 eV and -5.77 eV / -3.82 eV for PyB-2H and PyB-2F, respectively. This indicates good compatibility between PyB-2H and PyB-2F and common polymer donor materials (such as PBDB-T), suggesting that devices based on PyB-2H and PyB-2F are likely to achieve excellent photovoltaic performance.

[0066] Organic solar cells were fabricated using the acceptor materials PyB-2H and PyB-2F prepared in Examples 1 and 2, respectively. The device structure was ITO / PEDOT:PSS / PBDB-T:small molecule acceptor / PDIN / Ag. Figure 3 As shown, the organic solar cell fabricated by blending the acceptor material PyB-2H with the commonly used donor material PBDB-T exhibits an open-circuit voltage of 0.910V and a short-circuit current of 6.84mA / cm². 2The fill factor was 47.06%, and the power conversion efficiency was 2.93%. Organic solar cells fabricated by blending the acceptor material PyB-2F with the commonly used donor material PBDB-T exhibited an open-circuit voltage of 0.823V and a short-circuit current of 10.68mA / cm². 2 The fill factor is 55.63%, and the energy conversion efficiency is 4.89%.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A two-dimensional π-bridged pyrene nucleus small molecule acceptor material, with the structure of general formula (I): in: Ar 1 It is one of the following groups: Where R 1 For C1-C 20 alkyl; Ar 2 It is one of the following groups:

2. The small molecule receptor material according to claim 1, characterized in that: When Ar 1 for And Ar 2 for At that time, R 1 It is 2-octyldodecyl, and its structure is as shown in general formula (II):

3. A method for preparing the material according to claim 1, characterized in that, Including the following steps: Step 1: 3,10-dibromo-1,9-diisopropylpyrene (a) is coupled with a compound of general formula (III) via Stille coupling to obtain intermediate (b); Step 2: Intermediate (b) and POCl3 are formylated in 1,2-dichloroethane / DMF to obtain aldehyde compound (c); Step 3: Compound (c) and compound of general formula (IV) are subjected to Knauvengel condensation to obtain the target product (I); 4. The method according to claim 3, characterized in that: Step 1 involves reflux for 12-24 hours under argon protection, tetra(triphenylphosphine)palladium catalysis, and toluene solvent.

5. The method according to claim 3, characterized in that: Step 2: Add POCl3 dropwise to an ice-water bath, stir at room temperature for 0.5 hours, and then reflux for 24 hours.

6. The method according to claim 3, characterized in that: Step 3: Reflux in chloroform / pyridine system for 20 hours, followed by methanol precipitation for purification.

7. A method for preparing compound (II) according to claim 2, characterized in that, Including the following steps: Step 1: Compound 1 is coupled with 4-(3-(2-octyldodecyloxy)phenyl)-2-tributyltinylthiophene via Stille coupling to obtain compound 2; Step 2: Compound 2 is formylated by Vilsmeier to obtain compound 3; Step 3: Compound 3 is condensed with 5,6-difluoro-3-(dicyanomethylene)indone to give (II); 8. The use of any one of the materials described in claims 1-7 in the acceptor layer of an organic solar cell.

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