A non-fused asymmetric indole derivative core small molecule receptor material and preparation method thereof

Abstract

The present invention discloses a non-fused asymmetric indole derivative core small molecule receptor material and a preparation method thereof, which relates to the field of organic solar cell materials. The receptor material of the present invention has the general structural formula: #imgabs0# wherein Ar 1 and Ar 3 is an independent aromatic group, Ar 2 With Ar 1 Same aromatic group, one less β-linking site, R 1 C1-C 20 The small molecule receptor material of the present invention uses an indole derivative as a core, has a non-fused asymmetric chemical structure, is easy to synthesize, and has a significant red-shift in its absorption spectrum, which can improve the utilization rate of sunlight and significantly increase the photocurrent of organic solar cells. When used in solar cells, it has the advantages of high energy conversion efficiency and low cost.

Description

Technical Field

[0001] The present invention relates to the field of organic solar cells, and in particular to a non-condensed asymmetric indole derivative core small molecule receptor material and a preparation method thereof. Background Art

[0002] Solar energy is a clean energy source that is inexhaustible. 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 research focus for scientists. Non-fullerene acceptors (NFAs) have gradually stood out among acceptor materials due to their unique advantages, such as: large adjustable band gap space, light absorption edge that can extend to the near-infrared region, strong energy level tunability, high open-circuit voltage, and easy adjustment of molecular planarity and crystallinity. Small molecule non-fullerene acceptor materials (SMAs) have the characteristics of clear molecular structure, better batch-to-batch reproducibility, high purity, easy adjustment of absorption spectrum and chemical energy level. Their status in the field of organic solar cells has risen rapidly and has become one of the current research hotspots. So far, the power conversion efficiency (PCE) of organic solar cells based on small molecule acceptor materials has exceeded 19%.

[0003] Small molecule receptor materials, such as the classic ITIC and Y6, generally adopt a fused ring structure skeleton, and the synthesis is generally complicated, and the long synthesis route leads to a low overall yield, which greatly increases the synthesis cost of the material, thereby hindering its industrial synthesis. Compared with fused ring small molecule receptor materials, non-fused small molecule receptors are currently limited by their small molecular types and low efficiency, so it is very important to develop new and efficient non-fused ring small molecule receptors. At the same time, broadening the absorption spectrum is extremely important for improving photocurrent and energy conversion efficiency. In the previous work, the applicant developed a series of indole derivative core small molecule receptor materials with a fused structure (application number: CN202010371715.3 and application number: CN202110937754.X). This type of receptor material exhibits a broadened absorption spectrum and higher energy conversion efficiency due to the indole derivative with a strong electron donating unit as the core, but the synthesis route still needs to be further simplified to reduce the synthesis cost. Therefore, in order to achieve this goal, it is urgent to provide a non-fused indole derivative core small molecule receptor material, which is particularly important to broaden the absorption spectrum, improve the photocurrent and energy conversion efficiency, and reduce the cost to solve the shortcomings of the existing technology. Summary of the Invention

[0004] One of the purposes of the present invention is to provide a non-fused asymmetric indole derivative core small molecule receptor material.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A non-fused asymmetric indole derivative core small molecule receptor material, the general structural formula of which is:

[0007]

[0008] In the general formula (I), Ar 1 One of the following structural units:

[0009] R 2 H, or C1-C 20 Alkyl;

[0010] Ar 2 The structural formula of Ar 1 Same, but with one less attachment site at the β position:

[0011] R 2 H, or C1-C 20 Alkyl;

[0012] Ar 3 One of the following structural units:

[0013]

[0014] R 1 C1-C 20 of alkyl.

[0015] Another object of the present invention is to provide a method for preparing the non-fused asymmetric indole derivative core small molecule receptor material, comprising the following steps:

[0016] Step 1: 1,4-dibromo-2-nitrobenzene (a) and a compound of formula (III) are subjected to Stille coupling reaction to obtain a compound of formula (b);

[0017]

[0018] Step 2: Reducing the compound of formula (b) and triphenylphosphine in an organic solvent to obtain a compound of formula (c);

[0019]

[0020] Step 3: subjecting the compound of formula (c) to an N-alkylation reaction to obtain a compound of formula (d);

[0021]

[0022] Step 4: Formylation of the compound of formula (d) to obtain a compound of formula (e);

[0023]

[0024] Step 5: subjecting the compound of formula (e) to a Knoevenagel condensation reaction with the compound of formula (IV) to obtain a compound of formula (I);

[0025]

[0026] Thus, the present invention provides a non-fused asymmetric indole derivative core small molecule acceptor material. The absorption spectrum of the non-fused asymmetric indole derivative core is significantly red-shifted compared to existing similar molecules without nitrogen atoms (such as ITIC and IT-4F). Compared with existing fused ring small molecule acceptor materials containing nitrogen atoms (such as Y6), the synthesis cost is significantly reduced. Therefore, the non-fused asymmetric indole derivative core small molecule acceptor material of the present invention can achieve both high energy conversion efficiency and reduced cost when applied to organic solar cells, facilitating commercial application.

[0027] Preferably, in step 1, in a protective atmosphere, 1,4-dibromo-2-nitrobenzene (a), a compound of formula (III), and toluene are placed in a reactor, and then tetrakis(triphenylphosphine)palladium is added, refluxed, cooled, poured into water, extracted with dichloromethane, the solvent is removed, and purified by column chromatography to obtain a compound of formula (b).

[0028] More preferably, the toluene is purified toluene.

[0029] Preferably, in step 2, under an argon atmosphere, the compound of general formula (b) is subjected to a reductive ring-closure reaction with triphenylphosphine in an organic solvent to obtain a compound of general formula (c).

[0030] More preferably, the organic solvent used is chlorobenzene.

[0031] Preferably, in step three, under an argon atmosphere, the compound of formula (c), brominated alkane, potassium carbonate and DMF are placed in a reactor, refluxed, cooled to room temperature, filtered, the solvent removed, and purified by column chromatography to obtain a compound of formula (d).

[0032] More preferably, the reaction temperature is 140°C.

[0033] Preferably, in step 4, in an argon atmosphere, the compound of general formula (d), 1,2-dichloroethane and DMF are placed in a reactor, phosphorus oxychloride is added under an ice-water bath, stirred, refluxed, cooled, and then an aqueous solution is added, extracted with dichloromethane, the solvent is removed by rotation, and purified by column chromatography to obtain a compound having general formula (e).

[0034] More preferably, the mixture is stirred at room temperature for 1 h before the reflux reaction.

[0035] Preferably, step five: sequentially add the compound of formula (e), the compound of formula (IV) and chloroform to a reactor, add pyridine under nitrogen protection, heat to reflux for reaction, cool and precipitate with methanol, and purify by column chromatography to obtain a compound of formula (II).

[0036] More preferably, the reflux time is 24 hours.

[0037] Another object of the present invention is to provide a non-fused asymmetric indole derivative core small molecule receptor material having a chemical structure of general formula (II):

[0038]

[0039] The method for preparing the above-mentioned non-fused asymmetric indole derivative core small molecule receptor material comprises the following steps:

[0040] Step 1: Compound 1, 6-undecyl-2-tributyltin-thieno[3,2-b]thiophene, and a toluene solution were added to a reactor, and tetrakis(triphenylphosphine)palladium was added under argon protection. The reaction was refluxed for 24 hours, cooled, poured into water, extracted with dichloromethane, and the solvent was removed by vortexing. The product was purified by column chromatography to obtain compound 2;

[0041]

[0042] Step 2: Compound 2, triphenylphosphine and chlorobenzene were added to a reactor, refluxed for 24 hours, cooled, and the solvent was removed. The mixture was purified by column chromatography to obtain compound 3;

[0043]

[0044] Step 3: Compound 3, bromoalkane, potassium carbonate and DMF were added to the reactor and refluxed for 20 hours. After cooling, the mixture was poured into water, extracted with dichloromethane, the solvent was removed by vortexing, and purified by column chromatography to obtain compound 4;

[0045]

[0046] Step 4: Compound 4, 1,2-dichloroethane and DMF were added to the reactor under argon protection, and phosphorus oxychloride was added dropwise at 0°C. After stirring at room temperature for 1 hour, the mixture was refluxed for 20 hours. After cooling, the mixture was added to water, extracted with dichloromethane, and the solvent was removed by vortexing. The mixture was purified by column chromatography to obtain compound 5;

[0047]

[0048] Step 5: Compound 5, 5,6-difluoro-3-(dicyanomethylidene)indone and chloroform were added to the reactor in sequence, pyridine was added under nitrogen protection, and the mixture was heated to reflux for 24 hours. After cooling, the mixture was precipitated with methanol and purified by column chromatography to obtain compound (II);

[0049]

[0050] Another object of the present invention is to provide an application of the above-mentioned non-condensed asymmetric indole derivative core small molecule acceptor material in organic solar cells.

[0051] Beneficial effects of the present invention:

[0052] The present invention provides a non-fused asymmetric indole derivative core small molecule receptor material and its preparation method and application. The receptor material of the present invention has the general structural formula:

[0053] Among them, Ar 1 and Ar 3 is an independent aromatic group, Ar 2 Has the same aromatic group as Ar1, but with one less β-linking site, R 1 C1-C 20 Compared with the prior art, the present invention has the following characteristics:

[0054] 1. It has a non-condensed chemical structure, is easy to synthesize, and has low cost;

[0055] 2. Absorption spectrum with significant red shift;

[0056] 3. The absorption range is greatly broadened, which improves the utilization rate of sunlight by organic solar cells;

[0057] 4. The short-circuit current of organic solar cells is significantly improved;

[0058] 5. Improved the energy conversion efficiency of organic solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The present invention is further described with reference to the accompanying drawings, but the embodiments in the accompanying drawings do not constitute any limitation to the present invention.

[0060] Figure 1 The chloroform dilute solutions of the receptor materials TT-2F and TT-2Cl prepared in Example 1 and Example 2 (10 - 5 M) and absorption spectra in thin film state;

[0061] Figure 2Cyclic voltammograms of the acceptor materials TT-2F and TT-2Cl prepared in Example 1 and Example 2;

[0062] Figure 3 JV curves of organic solar cells prepared by blending the acceptor materials TT-2F and TT-2Cl prepared in Example 1 and Example 2 with the donor material PM6. DETAILED DESCRIPTION

[0063] The present invention is further described with reference to the following examples.

[0064] Example 1:

[0065] The preparation method of the non-fused asymmetric indole derivative core small molecule receptor material TT-2F comprises the following specific steps:

[0066]

[0067] (1) Synthesis of Compound 2: 1,4-Dibromo-2-nitrobenzene (500 mg, 1.78 mmol), 6-undecyl-2-tributyltin-thieno[3,2-b]thiophene (2.30 g, 4.01 mmol), and 25 mL of toluene were added to a 100 mL single-necked flask. Ar was added, and 30 mg of Pd(PPh3)4 was added. The mixture was reacted at 90°C in the dark for 24 h. The mixture was cooled to room temperature, poured into 100 mL of water, extracted with dichloromethane, dried over anhydrous MgSO4, concentrated, and separated by column chromatography (petroleum ether as eluent) to obtain 880 mg of a yellow solid (yield: 69.8%).

[0068] (2) Synthesis of Compound 3: To a 100 mL single-necked flask, 15 mL of chlorobenzene, compound 2 (846 mg, 1.19 mmol), and triphenylphosphine (787 mg, 3.00 mmol) were added. Ar-protected, the reaction was carried out at 140°C in the dark for 24 h. After cooling to room temperature, the solvent was removed and the product was separated by column chromatography (petroleum ether:dichloromethane = 5:1) as the eluent to obtain 245 mg of a white solid (yield: 30.5%).

[0069] (3) Synthesis of Compound 4: 20 mL of DMF (dried), compound 3, 1-bromo-2-octyldodecane (553 mg, 1.53 mmol), and anhydrous potassium carbonate (352 mg, 2.55 mmol) were added to a 100 mL single-necked flask. Ar protection was applied and the reaction was carried out at 140°C for 20 h. The mixture was cooled to room temperature, poured into water, extracted with DCM, and washed with water until the volume of the organic phase remained essentially unchanged. The mixture was dried over anhydrous MgSO4, filtered, concentrated, and separated by column chromatography (petroleum ether as eluent) to obtain 278 mg of a yellow solid (yield: approximately 80.0%). 1HNMR (CDCl3, 400MHz, δ / ppm): 7.69 (s, 1H), 7.61 (s, 1H), 7.48 (d, J = 8.8Hz, 2H), 7.00 (s, 1H), 6.95 (s, 1H), 4.23 (d,J=7.3Hz,2H),2.81-2.72(m,4H),2.18(br,1H),1.83-1.76(m,4H),1.49-1.09(m,61H),0.93-0.80(m,12H).

[0070] (4) Synthesis of Compound 5: 25 mL of 1,2-dichloroethane (dried), compound 4 (245 mg, 0.26 mmol), and 2 mL of DMF (purified) were added to a 100 mL two-necked flask. Ar was used for protection. Phosphorus oxychloride was added at 0°C and stirred for 30 min. The mixture was reacted at 86°C for 20 h. The mixture was cooled to room temperature and added dropwise to a saturated aqueous Na2CO3 solution. The mixture was stirred until no bubbles were generated. The mixture was extracted with dichloromethane, dried over anhydrous MgSO4, concentrated, and separated by column chromatography (petroleum ether:dichloromethane = 1:1 as eluent) to obtain 224 mg of a red solid (yield: 85.2%). 1 H NMR (CDCl 3, 400MHz, δ / ppm):10.14-10.06(m,2H),7.77(d,J=7.5Hz,1H),7.61(s,1H),7.57-7.49(m,2H),4.23(t,J=7.1Hz 2H),3.20-3.07(m,4H),2.13(br,1H),1.93-1.80(m,4H),1.50-1.11(m,61H),0.93-0.80(m,12H).

[0071] (5) Synthesis of TT-2F: To a 100 mL single-necked flask were added 20 mL of chloroform (purified), 5,6-difluoro-3-(dicyanomethylene)indone (95 mg, 0.42 mmol), and compound 5 (70 mg, 0.07 mmol). Ar protection was performed, and 0.5 mL of pyridine was added. The reaction was allowed to proceed at 70°C for 20 h. The mixture was cooled to room temperature, precipitated with methanol, and separated by column chromatography (petroleum ether:dichloromethane = 1:1 as eluent) to obtain 79 mg of a bluish-black solid (yield: 78.5%). 1 HNMR (CDCl 3,400MHz,δ / ppm):8.84(s,1H),8.62(s,1H),8.41(s,1H),8.26(s,1H),7.67-7.60(m,3H),7.40-7.29(m,3H),4.15(d,J=6.8Hz,2H), 3.18-3.03(m,2H),2.99-2.87(m,2H),2.01(br,1H),1.85-1.75(m,2H),1.73-1.66(m,2H),1.54-1.12(m,61H),0.92-0.78(m,12H).

[0072] Example 2:

[0073] The preparation method of the non-fused asymmetric indole derivative core small molecule receptor material TT-2Cl comprises the following steps:

[0074]

[0075] Synthesis of TT-2Cl: To a 100 mL single-necked flask was added 20 mL of chloroform (purified), 5,6-dichloro-3-(dicyanomethylidene)indone (125 mg, 0.47 mmol), and compound 5 (80 mg, 0.08 mmol). Ar protection was performed, and 0.5 mL of pyridine was added. The reaction was allowed to proceed at 70°C for 20 h. Cooling to room temperature allowed the product to precipitate with methanol. Column chromatography (petroleum ether:dichloromethane = 1:1 as eluent) afforded 69 mg of a black solid (yield: 57.5%). 1 H NMR (CDCl 3, 400MHz, δ / ppm):8.83(s,1H),8.63(s,1H),8.59(s,1H),8.46(s,1H),7.85( s,1H),7.83(s,1H),7.58(d,J=8.2Hz,1H),7.32-7.27(m,2H),7.25(s,1H),4 .13(d,J=6.2Hz,2H),3.15-3.00(m,2H),2.96-2.85(m,2H),2.02(br,1H),1. 86-1.74(m,2H),1.74-1.63(m,2H),1.43-1.20(m,61H),0.90-0.80(m,12H).

[0076] The UV-visible absorption spectra of the two small molecule receptor materials TT-2F and TT-2Cl prepared in Example 1 and Example 2 in the chloroform dilute solution and thin film state are as follows: Figure 1As shown. The maximum absorption wavelengths of TT-2F and TT-2Cl in dilute chloroform solution are 678nm and 690nm, respectively, and TT-2Cl undergoes a red shift of 12nm. The maximum film absorption peaks of the small molecule receptors TT-2F and TT-2Cl are 718nm and 750nm, respectively, which are significantly red-shifted compared with the solution absorption spectrum, which is mainly due to the stronger π-π stacking of TT-2Cl. The optical band gaps of TT-2F and TT-2Cl are 1.52eV and 1.50eV, respectively. Compared with the small molecule receptor material IT-4F with a fused ring structure, the absorption peaks of the non-fused asymmetric indole derivative small molecule receptor materials TT-2F and TT-2Cl prepared in Example 1 and Example 2 are red-shifted by about 20nm, and have a significantly broadened absorption spectrum, which is conducive to obtaining higher photocurrent and energy conversion efficiency in the device.

[0077] The cyclic voltammetry curves of the two small molecule receptor materials TT-2F and TT-2Cl prepared in Example 1 and Example 2 are shown in FIG. Figure 2 As shown, the oxidation potentials (E ox on ) is 0.89V and 0.77V, the reduction potential (E red on ) is -0.92V and -0.93V. According to the empirical formula E HOMO =-(E ox on +4.8)(eV) and E LUMO =-(E red on Calculations using a 1.5-μm CMOS (0.5-μm CMOS) (eV) yielded HOMO / LUMO energy levels of -5.69 eV / -3.88 eV and -5.57 eV / -3.87 eV for TT-2F and TT-2Cl, respectively. This indicates that TT-2F and TT-2Cl have good compatibility with common polymer donor materials (such as PM6), and devices based on TT-2F and TT-2Cl are expected to achieve excellent photovoltaic performance.

[0078] The acceptor material TT-2F prepared in Example 1 was used as the acceptor material to prepare an organic solar cell, and the device structure was ITO / PEDOT:PSS / PM6:TT-2F / PDINO / Al. Figure 3 As shown in the figure, after thermal annealing optimization, the open circuit voltage of the best device prepared by blending the acceptor material TT-2F with the commonly used donor material PM6 is 0.935V and the short circuit current is 19.21mA / cm 2 , the filling factor is 59.40% and the energy conversion efficiency is 10.67%.

[0079] 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 the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a compound of formula (II), characterized in that: The following steps are involved: Step 1: Compound 1, 6-undecyl-2-tributyltin-thieno[3,2-b]thiophene, and toluene were added to a reactor, and tetrakis(triphenylphosphine)palladium was added under argon protection. The reaction was refluxed for 24 hours, cooled, poured into water, extracted with dichloromethane, and the solvent was removed by vortexing. The product was purified by column chromatography to obtain compound 2; Step 2: Compound 2, triphenylphosphine and chlorobenzene were added to a reactor, refluxed for 24 hours, cooled, and the solvent was removed. The mixture was purified by column chromatography to obtain compound 3; Step 3: Compound 3, bromoalkane, potassium carbonate and DMF were added to the reactor and refluxed for 20 hours. After cooling, the mixture was poured into water, extracted with dichloromethane, the solvent was removed by vortexing, and purified by column chromatography to obtain compound 4; Step 4: Compound 4, 1,2-dichloroethane and DMF were added to the reactor under argon protection, and phosphorus oxychloride was added dropwise at 0°C. After stirring at room temperature for 1 hour, the mixture was refluxed for 20 hours. After cooling, the mixture was added to water, extracted with dichloromethane, and the solvent was removed by vortexing. The mixture was purified by column chromatography to obtain compound 5; Step 5: Compound 5, 5,6-difluoro-3-(dicyanomethylidene)indone and chloroform were added to the reactor in sequence, pyridine was added under nitrogen protection, and the mixture was heated to reflux for 24 hours. After cooling, the mixture was precipitated with methanol and purified by column chromatography to obtain compound (II);

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