Oligomeric small molecule donor compounds, methods of making and using the same

Abstract

The application provides an oligomeric small-molecule donor compound, a preparation method and application thereof. The oligomeric small-molecule donor compound belongs to a new type of long-conjugated organic small-molecule donor material containing a connecting unit, two or more than two efficient organic small-molecule donors are combined into one, the conjugated length is prolonged, and a series of novel oligomeric small-molecule donor materials are synthesized. The oligomeric small-molecule donor compound has good batch repeatability and good film-forming property. The oligomeric small-molecule donor compound prolongs the conjugated length, has excellent ultraviolet-visible light absorption performance, has strong interaction and aggregation between molecules, can realize good phase separation with a non-fullerene acceptor, has suitable electronic energy level, and is suitable for being used as an electron donor material in an organic solar cell.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of organic solar device materials, and particularly relates to an oligomeric small-molecule donor compound and a preparation method and application thereof. BACKGROUND

[0002] Organic solar cells convert clean and renewable solar energy into electrical energy since 1990s. As a promising green energy technology, organic solar cells have broad application and development prospects in Internet of Things sensing devices such as electronic tags, building and equipment integration, automobile glass and wearable devices, etc. due to the advantages of low cost, light weight, simple preparation process and large-area flexible preparation.

[0003] An organic solar cell generally consists of five parts: an anode, an anode buffer layer, an active layer, a cathode buffer layer and a cathode. The active layer generally contains a donor material and an acceptor material. The selection of the active layer material is crucial to the efficiency of the organic solar cell device.

[0004] In recent years, the power conversion efficiency (PCE) of organic solar cells based on conjugated polymer as donor and non-fullerene derivative as acceptor has exceeded 20% (Z. Zheng, J. Wang, P. Bi, J. Ren, Y. Wang, Y. Yang, X. Liu, S. Zhang, J. Hou, Joule 2022, 6, 171; H. Lu, D. Li, W. Liu, G. Ran, H. Wu, N. Wei, Z. Tang, Y. Liu, W. Zhang, Z. Bo, Angew. Chem. Int. Ed. 2024, e202407007; S. Guan, Y. Li, C. Xu, N. Yin, C. Xu, C. Wang, M. Wang, Y. Xu, Q. Chen, D. Wang, L. Zuo, H. Chen, Adv. Mater. 2024, 2400342; Y. Sun, L. Wang, C. Guo, J. Xiao, C. Liu, C. Chen, W. Xia, Z. Gan, J. Cheng, J. Zhou, Z. Chen, J. Zhou, D. Liu, T. Wang, W. Li, J. Am. Chem. Soc. 2024, 146, 12011.). Since conjugated polymers are long-chain structures formed by chemical polymerization reactions, their molecular weight and molecular weight distribution are usually difficult to control accurately, resulting in structures with uneven molecular weight distribution during the preparation process. This unevenness can affect electron transport, light absorption, and the crystallinity of the material, thereby affecting device performance. Chinese patent document CN115449057A discloses a kind of based on double rhodanine conjugated polymer, based on double rhodanine conjugated polymer includes double rhodanine center core and electron-donating group, electron-donating end group is connected at the two ends of the center core, its preparation process is to take tetramethylene diamine and its homologues as raw material, cyclization reaction obtains double rhodanine center core, then introduces electron-donating group structure through Knoevenagel reaction, finally, double rhodanine conjugated polymer donor material is obtained by Stille coupling. However, there may be inconsistencies in performance between different batches due to small differences in polymerization conditions. In addition, structural defects may occur in the polymer, such as uneven end groups, wide chain length distribution, etc., which can cause fluctuations in its optoelectronic properties and affect the repeatability of the device.

[0005] In recent years, the power conversion efficiency (PCE) of organic solar cells based on small organic molecules as donors and non-fullerene derivatives as acceptors has exceeded 18%. However, there are still some defects in using small organic molecules as donor materials. Due to the short conjugation length, it is difficult to produce phase separation after blending with non-fullerene acceptors, and it is greatly affected by film preparation conditions and has poor stability, which limits the development of all-small-molecule organic solar cells. (H. Chen, D. Hu, Q. Yang, J. Gao, J. Fu, K. Yang, H. He, S. Chen, Z. Kan, T. Duan, C. Yang, J. Ouyang, Z. Xiao, K. Sun, S. Lu, Joule 2019, 3, 3034; J. Ge, L. Xie, R. Peng, Z. Ge, Advanced Materials 2023, 35, 2206566.). Chinese patent document CN104926830A discloses a two-dimensional conjugated benzodithiophene compound and its preparation method and use. The compound of the invention has a wide visible region absorption and suitable energy level, and the energy conversion efficiency of the solar cell prepared from the compound exceeds 8%, showing excellent photovoltaic performance. However, small molecule donor molecules have too small molecular weight and insufficient conjugation degree, which cannot be preferentially self-aggregated, are easy to diffuse, and result in difficult morphology control and poor stability.

[0006] Oligomeric small organic molecules are expected to solve the problems of small organic molecules as donor materials. Therefore, it is of great significance to develop oligomeric small organic molecules to effectively improve the photovoltaic performance of solar cells. SUMMARY

[0007] In view of the deficiencies in the prior art, the present application provides an oligomeric small molecule donor compound and its preparation method and application. The oligomeric small molecule donor compound of the present application has good batch repeatability and good film-forming property; the oligomeric small molecule donor compound of the present application prolongs the conjugation length, has excellent ultraviolet-visible light absorption performance, has strong interaction and aggregation between molecules, can realize good phase separation with non-fullerene acceptors, and has suitable electronic energy level, suitable for used as electron donor material in organic solar cells.

[0008] The technical scheme adopted by the present application is as follows:

[0009] An oligomeric small molecule donor compound has a structure as shown in formula I or II:

[0010]

[0011]

[0012] In formula I or II,

[0013] R1is selected from any one of 2,5-carboxylate thienyl, 3,4-carboxylate thienyl, 1,4-carboxylate phenyl, 1,3-carboxylate phenyl or 1,2-carboxylate phenyl;

[0014] Ar is selected from one of thienyl, thienyl derivative, dithienyl, dithienyl derivative, thienodithienyl derivative, dithienothiophenyl, dithienothiophenyl derivative, dithienothiophenyl derivative, pyrrolodithienyl, pyrrolodithienyl derivative, furanodithienyl or furanodithienyl derivative;

[0015] EG is selected from any one of the following structures:

[0016]

[0017] wherein R2, R2', R2" are independently selected from one of C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy, C1-C4thioalkyl, C4-C8cycloalkyl, C6-C10aryl or halogen; 30 30 30 30 30

[0018] Electron withdrawing group A1 is selected from one of the following structures:

[0019]

[0020] wherein R3 is any one of C1-C4alkyl; 30

[0021] Electron withdrawing group A2 is selected from one of the following structures:

[0022]

[0023] wherein R4 is any one of C1-C4alkyl. 30

[0024] According to the present application, preferably, the oligomeric small molecule donor compound has the following structure:

[0025]

[0026]

[0027] The preparation method of the oligomeric small molecule donor compound comprises the steps of:

[0028] (1) dissolving compound 1 in ethanol, adding potassium hydroxide ethanol solution, and obtaining compound 2 through reaction; ​​​​​​​

[0029] (2) Compound 2, chloroalkyl alcohol is dissolved in N'N-dimethylformamide, and compound 3 is obtained by reaction;

[0030] (3) Compound 4, compound 5 and tetrakis (triphenylphosphine) palladium are dispersed in chlorobenzene, and compound 6 is obtained by microwave reaction;

[0031] (4) Compound 6 is dissolved in chloroform solvent, and dehydroxy compound 3, compound 3 and piperidine are added, and compound 7 is obtained by reaction;

[0032] (5) Compound 7, dicarboxylic acid compound, N,N'-dicyclohexyl carbonyl imide and 4-dimethylamino pyridine are dispersed in chloroform, and then N,N'-dicyclohexyl carbonyl imide is added, and the oligomer small molecule donor compound is obtained by reaction.

[0033] Compound 1 is selected from one of the following compounds:

[0034]

[0035] In the chloroalkyl alcohol, the alkyl group is C1-C 30 Alkyl group;

[0036] Compound 4 is (CH3) 3Sn-EG-Sn (CH3) 3, wherein EG is the same as EG in formula I or II;

[0037] Compound 5 is one of thiophene, thiophene derivative, bithiophene, bithiophene derivative, thienobithiophene derivative, bithiophene derivative, benzodithiophene derivative, pyrrolobithiophene, pyrrolobithiophene derivative, furanobithiophene or furanobithiophene derivative;

[0038] The dicarboxylic acid compound is any one of 2,5-thiophene dicarboxylic acid, 3,4-thiophene dicarboxylic acid, 1,4-phenyl dicarboxylic acid, 1,3-phenyl dicarboxylic acid or 1,2-phenyl dicarboxylic acid.

[0039] According to the application, compound 1, compound 2, compound 3, compound 4, compound 5, compound 6 and compound 7 respectively have the following structures

[0040]

[0041]

[0042] According to the application, the chloroalkyl alcohol is 6-chloro-1-hexanol; the dicarboxylic acid compound is 2,5-thiophene dicarboxylic acid; and the dehydroxy compound 3 has the following structure:

[0043]

[0044] According to the application, in step (1), the molar ratio of compound 1 to ethanol is 2-8 mol / L; the molar concentration of potassium hydroxide ethanol solution is 4-5 mol / L; the molar ratio of compound 1 to potassium hydroxide is 1:1.01-1.25; the reaction temperature is 60-100℃, and the reaction time is 1-3 h, and the reaction is carried out under stirring, nitrogen or argon atmosphere.

[0045] According to the application, in step (1), the reaction liquid obtained is treated as follows: the reaction liquid is washed with cold ethanol, and dried to obtain compound 2.

[0046] According to the application, in step (2), the molar ratio of compound 2 to N,N-dimethylformamide is 0.5-5 mol / L; the molar ratio of compound 2 to chloroalkyl alcohol is 1:1.0-1.5; the reaction temperature is 140-150℃, and the reaction time is 2-6 h, and the reaction is carried out under reflux stirring, nitrogen or argon atmosphere.

[0047] According to the application, in step (2), the reaction liquid obtained is treated as follows: the reaction liquid is extracted with ethyl acetate, and the organic phase is taken, and the solvent is rotary evaporated to obtain the crude product; then, column chromatography is used to separate to obtain compound 3.

[0048] According to the application, in step (3), the molar ratio of compound 4, compound 5 and tetrakis(triphenylphosphine)palladium is 1:2.5-3:0.05-0.10; the molar ratio of compound 4 to chlorobenzene is 0.01-1 mol / L; the microwave reaction temperature is 150-160℃, the microwave power is 70 W, the microwave reaction time is 2-6 h, and the microwave reaction atmosphere is nitrogen or argon.

[0049] According to the application, in step (3), the reaction liquid obtained is treated as follows: the reaction liquid is extracted with dichloromethane, and the organic phase is taken, and the solvent is rotary evaporated, and then column chromatography is used to separate to obtain compound 6.

[0050] According to the application, in step (4), the molar ratio of compound 6 to chloroform is 0.001-0.1 mol / L; the molar ratio of compound 6, dehydroxylated compound 3, compound 3 and piperidine is 1:3-4:3-4:0.001-0.15; the reaction temperature is 50-70℃, and the reaction time is 10-20 h, and the reaction is carried out under stirring, nitrogen or argon atmosphere.

[0051] According to the application, preferably, in step (4), the reaction liquid obtained in the reaction is treated as follows: the reaction liquid is extracted with chloroform, the organic layer is washed with water, dried over anhydrous magnesium sulfate, the organic solvent is removed by rotary evaporation, and then the compound 7 is obtained by column chromatography.

[0052] According to the application, preferably, in step (5), the molar ratio of the dicarboxylic acid compound, the compound 7, N,N'-dicyclohexyl carbodiimide and 4-dimethylamino pyridine is 1:1.8-2.2:4-4.2:0.1-0.2; the molar amount of the compound 7 and the volume of chloroform are in the ratio of 0.001-0.1 mol / L; the reaction temperature after the compound 7, the dicarboxylic acid compound, N,N'-dicyclohexyl carbodiimide and 4-dimethylamino pyridine are fully dispersed in chloroform is room temperature, the reaction time is 8-12 h, and the reaction is carried out under stirring, nitrogen or argon atmosphere; the reaction temperature after the addition of N,N'-dicyclohexyl carbodiimide is room temperature, the reaction time is 8-12 h, and the reaction is carried out under stirring, nitrogen or argon atmosphere.

[0053] According to the application, preferably, in step (5), the reaction liquid obtained in the reaction is treated as follows: the reaction liquid is extracted with chloroform, the organic layer is washed with water, dried over anhydrous magnesium sulfate, the organic solvent is removed by rotary evaporation, and then the low-molecular oligomer donor compound is obtained by column chromatography.

[0054] The low-molecular oligomer donor compound is applied as an active layer electron donor material for organic solar cells for light capture.

[0055] The technical features and advantages of the application are as follows:

[0056] 1. The low-molecular oligomer donor compound of the application is prepared by a solution method, has a simple structure, is easy to synthesize, has a high yield, and has good batch repeatability; can be dissolved in chloroform, tetrahydrofuran and chlorobenzene and other organic solvents, and has good film forming property.

[0057] 2.The novel oligomeric small molecule donor compound provided by the application belongs to a brand new long conjugated organic small molecule donor material containing a connecting unit, combines two efficient organic small molecule donors in one, prolongs the conjugated length, and synthesizes a series of novel oligomeric small molecule donor materials.The oligomeric small molecule donor compound of the application has the main skeleton structure of a star small molecule donor, has excellent ultraviolet-visible light absorption performance, has strong absorption in the range of 400-700 nm, and has obvious absorption red shift of thin film absorption compared with solution absorption, indicating that there is strong interaction and aggregation between molecules.The oligomeric small molecule donor compound of the application has suitable electronic energy levels and is suitable for use in electron donor materials in organic solar cells.Meanwhile, the introduction of the connecting unit will be beneficial to improving the phase separation of the active layer, and the crystallinity of the oligomeric small molecule can be adjusted by the alkyl length of the connecting unit, the stability of the active layer of the all-small molecule solar cell is improved, and the mechanical strength of the cell is effectively improved.

[0058] 3.Compared with small molecules and polymers, the oligomer has better structure controllability, film forming property and flexibility of performance regulation.Compared with polymers, the molecular weight of the oligomer is easier to control, the crystallinity is better, the thin film formed is more uniform, and the device performance is more stable;compared with small molecules, the oligomer has moderate molecular weight, maintains good solubility and tensile properties, and can realize the regulation of energy level and photoelectric performance by adjusting the polymerization degree.In addition, the environmental stability and device repeatability of the oligomer are better than those of the small molecule, and thus the oligomer has better comprehensive performance. BRIEF DESCRIPTION OF DRAWINGS

[0059] Figure 1 The H NMR of the compound 3 prepared in the embodiment 1 of the application is as follows: 1 H NMR.

[0060] Figure 2 The H NMR of the compound 3 prepared in the embodiment 1 of the application is as follows: 13 C NMR.

[0061] Figure 3 The H NMR of the compound 6 prepared in the embodiment 1 of the application is as follows: 1 H NMR.

[0062] Figure 4 The H NMR of the compound 6 prepared in the embodiment 1 of the application is as follows: 13 C NMR.

[0063] Figure 5 The H NMR of the compound 7 prepared in the embodiment 1 of the application is as follows: 1 H NMR.

[0064] Figure 6 The H NMR of the compound 7 prepared in the embodiment 1 of the application is as follows: 13C NMR.

[0065] Figure 7 The mass spectrum of the new oligomeric organic small molecule donor 2BTR-Cl-T prepared in Example 1 of the present application is shown in Figure 1. 1 HNMR.

[0066] Figure 8 The mass spectrum of the new oligomeric organic small molecule donor 2BTR-Cl-T prepared in Example 1 of the present application is shown in Figure 1.

[0067] Figure 9 The ultraviolet-visible absorption spectrum of the new oligomeric organic small molecule donor 2BTR-Cl-T prepared in Example 1 of the present application in chloroform solution and in thin film state is shown in Figure 2.

[0068] Figure 10 The cyclic voltammogram of the new oligomeric organic small molecule donor 2BTR-Cl-T prepared in Example 1 of the present application is shown in Figure 3.

[0069] Figure 11 The temperature-dependent ultraviolet-visible absorption spectrum of the new oligomeric organic small molecule donor 2BTR-Cl-T prepared in Example 1 of the present application is shown in Figure 4.

[0070] Figure 12 The temperature-dependent ultraviolet-visible absorption spectrum of the organic small molecule donor BTR-Cl is shown in Figure 5.

[0071] Figure 13 The synthetic route of the new oligomeric organic small molecule donor 2BTR-Cl-T prepared in Example 1 of the present application is shown in Figure 6. DETAILED DESCRIPTION

[0072] In order to make the purpose, technical scheme and effect of the present application more clear and explicit, the present application is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0073] In order to make the above-mentioned purpose, features and advantages of the present application more obvious and easy to understand, the technical scheme of the present application is further described below in combination with the drawings and examples. However, the present application is not limited to the listed examples, but also includes any known changes within the scope of the claimed rights of the present application.

[0074] Example 1, synthesis of oligomeric organic small molecule donor 2BTR-Cl-T

[0075] An oligomeric small molecule donor compound (I-1) has the following structure:

[0076]

[0077] The synthetic route is as follows:Figure 13 The specific preparation method is as follows:

[0078] Step 1) Synthesis of compound 2;

[0079] Compound 1 (5.1 g, 38.1 mmol) was dissolved in 9 mL of an ethanol solution under a nitrogen atmosphere, 9 mL of a potassium hydroxide (2.2 g, 40.0 mmol) ethanol solution was slowly added at 80°C, and the reaction was stirred for 2 hours. After washing the reaction liquid twice with cold ethanol, it was naturally dried, and the obtained compound 2 was directly used for the next reaction.

[0080] Step 2) Synthesis of compound 3;

[0081] The crude product compound 2 (990 mg, 5.8 mmol) obtained in the previous step was dissolved in 5 mL of N’N-dimethylformamide, and was stirred at 145°C under a nitrogen atmosphere for 4 hours. After extraction with ethyl acetate, the organic phase was obtained, and the solvent was spin-dried. The obtained crude product was separated by column chromatography using petroleum ether / ethyl acetate (volume ratio 2:1) as the eluent, and finally compound 3 (300 mg, yield 25%) was obtained.

[0082] The nuclear magnetic resonance spectrum of compound 3 is as shown in Figure 1 and Figure 2 The structure confirmation data are as follows: 1 H NMR (400 MHz, CDCl3) δ 4.01-3.95 (m, 4H), 3.68-3.60 (t, J = 6.5 Hz, 2H), 1.71-1.61 (m, 2H), 1.61-1.53 (m, 2H), 1.47-1.37 (m, 4H). 13 C NMR (101 MHz, CDCl3) δ 201.24, 173.93, 62.76, 44.63, 35.36, 32.51, 26.64, 26.48, 25.23.

[0083] Step 3) Synthesis of compound 6;

[0084] Compound 4 (213 mg, 0.2 mmol), compound 5 (253 mg, 0.5 mmol), and tetrakis(triphenylphosphine)palladium (23 mg, 0.02 mol) were mixed, 8 mL of chlorobenzene was added, and the nitrogen was exchanged three times. The microwave power was 70 W, and the microwave reaction was carried out at 155°C for 4 hours. After the reaction was completed, dichloromethane was extracted, the organic phase was obtained, and the solvent was spin-dried. The obtained crude product was separated by column chromatography using petroleum ether / dichloromethane (volume ratio 1:2) as the eluent, and finally compound 6 (235 mg, yield 71%) was obtained.

[0085] Compound 6 NMR spectra as shown in Figure 3 and Figure 4 The structure confirmation data are as follows: 1 H NMR (400 MHz, CDC13) δ 9.90-9.87 (d, J = 1.0 Hz, 2H), 7.72-7.69 (dd, J = 4.0, 1.6 Hz, 2H), 7.59-7.31 (d, J = 77.2 Hz, 2H), 7.31-7.21 (s, 2H), 7.23-7.16 (m, 2H), 7.15-7.03 (m, 2H), 7.02-7.00 (d, J = 4.3 Hz, 2H), 3.02-2.48 (m, 12H), 1.79-1.65 (m, 10H), 1.39-1.23 (m, 40H), 1.04-0.88 (m, 24H). 13 C NMR (101 MHz, CDC13) δ 182.57, 146.01, 142.58, 142.25, 141.23, 138.72, 138.64, 138.06, 137.31, 136.86, 135.84, 135.49, 135.15, 129.65, 129.16, 128.70, 128.03, 125.91, 122.89, 118.52, 40.89, 32.53, 31.67, 30.39, 30.24, 29.72, 29.38, 29.27, 28.85, 23.07, 22.71, 22.62, 14.14, 14.11, 14.09, 10.95.

[0086] Step 4) Synthesis of compound 7;

[0087] Compound 6 (235 mg, 0.2 mmol) was dissolved in clean purified chloroform solvent (30 ml). Then 3-hexyl rhodanine (140 mg, 0.6 mmol), 3-hexyl alcohol rhodanine (141 mg, 0.6 mmol) and 5 drops of piperidine (0.0075 mol) were added. After that the reaction mixture was stirred at 60 °C for 12 hours under argon atmosphere. After stirring the reaction for 12 hours, the reaction mixture was extracted with chloroform three times. The organic layer was washed with water three times and dried with anhydrous magnesium sulfate. After removing the anhydrous magnesium sulfate by suction filtration, the organic solvent was removed by rotary evaporation to obtain the crude product which was separated by column chromatography on silica gel. The column chromatography separation eluent was chloroform:methanol = 98:2 (volume ratio), and finally the product compound 7 (106 mg, yield 35.6%) was obtained.

[0088] Compound 7 NMR spectra as shown in Figure 5 and Figure 6 The structure confirmation data are as follows: 1H NMR (400 MHz, CDC13) δ 7.75 - 7.69 (s, 2H), 7.43 - 7.34 (s, 2H), 7.29 - 7.19 (d, J=9.5 Hz, 4H), 7.13 - 7.05 (d, J=4.0 Hz, 2H), 7.01 - 6.94 (s, 2H), 6.93 - 6.86 (d, J=3.6 Hz, 2H), 4.11 - 3.97 (dt, J=10.4, 5.3 Hz, 4H), 3.66 - 3.61 (t, J=6.5 Hz, 2H), 2.97 - 2.88 (m, 4H), 2.78 - 2.71 (t, J=7.9 Hz, 4H), 2.71 - 2.63 (t, J=8.1 Hz, 4H), 1.85 - 1.77 (q, J=6.3 Hz, 2H), 1.70 - 1.64 (m, 12H), 1.43 - 0.86 (m, 77H). 13 C NMR (101 MHz, CDC13) δ 192.05, 167.41, 144.33, 141.84, 140.82, 138.49, 138.43, 137.78, 137.11, 136.92, 135.57, 135.47, 134.81, 129.76, 128.85, 128.01, 126.25, 124.83, 122.85, 122.16, 118.30, 62.77, 40.85, 32.57, 32.26, 31.75, 31.71, 31.34, 30.24, 29.98, 29.85, 29.42, 28.87, 26.92, 26.47, 25.94, 25.22, 23.12, 22.72, 22.86, 22.53, 14.26, 14.18, 14.02, 10.97.

[0089] Step 5) Synthesis of compound 2B TR-CI-T;

[0090] Compound 7 (50 mg, 0.025 mmol), 2,5-thiophenedicarboxylic acid (2.21 mg, 0.013 mmol), N,N'-dicyclohexylcarbodiimide (5.30 mg, 0.027 mmol) and 4-dimethylaminopyridine (0.31 mg, 0.002 mmol) were mixed, 12 mL of chloroform was added, and the reaction mixture was stirred at room temperature for 10 hours under an inert atmosphere of argon. After stirring at room temperature for 10 hours under an inert atmosphere of argon, N,N'-dicyclohexylcarbodiimide (5.30 mg, 0.027 mmol) was added again, and the reaction mixture was extracted with chloroform three times after stirring at room temperature for 10 hours under an inert atmosphere of argon. The organic layer was washed with water three times and dried over anhydrous magnesium sulfate. After removing the anhydrous magnesium sulfate by suction filtration, the organic solvent was removed by rotary evaporation to obtain a crude product, which was separated by column chromatography on silica gel using petroleum ether: chloroform = 1:2 (volume ratio) as an eluent to finally obtain the product compound 2BTR-CI-T (8 mg, yield 14%).

[0091] The nuclear magnetic resonance spectrum of compound 2BTR-CI-T is shown in Figure 7 The mass spectrum of compound 2BTR-CI-T is shown in Figure 8 The structure confirmation data of compound 2BTR-CI-T are as follows: 1 HNMR (400 MHz, CDC13) δ 7.76 - 7.74 (s, 2H), 7.74 - 7.66 (m, 4H), 7.35 - 7.32 (t, J = 4.0 Hz, 4H), 7.29 - 7.19 (s, 8H), 7.14 - 6.82 (m, 12H), 4.31 - 4.25 (t, J = 5.0 Hz, 4H), 4.08 - 4.00 (d, J = 11.2 Hz, 10H), 2.95 - 2.89 (m, 8H), 2.76 - 2.61 (dd, J = 28.4, 7.9 Hz, 16H), 2.25 - 2.19 (t, J = 7.6 Hz, 8H), 2.10 - 1.92 (d, J = 6.2 Hz, 16H), 1.86 - 0.68 (m, 160H). MS (MALDI-TOF) of 2BTR-CI-T m / z: [M+H]+calcd for C 210 H 253 CI4N4O8S 29 ,4032.016, found: 4032.435.

[0092] The nuclear magnetic resonance spectrum and the mass spectrum of compound 2BTP-CI-T show that compound 2BTP-CI-T is an oligomeric small molecule donor compound as described above.

[0093] Test Example 1, Processability of the oligomer of the present application and measurement of optical band gap using absorption spectrum

[0094] The oligomer prepared in Example 1 was mixed with various organic solvents, including chlorinated solvents such as chloroform, chlorobenzene and dichlorobenzene, and other solvents such as methanol, toluene and tetrahydrofuran. It was found that the oligomer had good solubility in chlorinated solvents. A high quality thin film with a thickness of 78 nm was prepared by spin-coating a chloroform solution of the oligomer with a concentration of 10 mg / mL onto a glass slide.

[0095] The absorption spectrum of the oligomer prepared in Example 1 was measured in chloroform solution (concentration of 0.01 mg / mL) and in film state, as shown in Figure 9 The optical band gap of the polymer was calculated using the empirical formula (E g opt = 1240 / λonset, where: E g opt is the optical band gap of the polymer; λonsetis the onset of the absorption spectrum in the long wavelength direction) and is shown in Table 1.

[0096] Table 1 Optical absorption data of oligomer 2BTR-Cl-T

[0097]

[0098] As shown in Figure 9 , there is strong absorption in the range of 400-700 nm, and the film absorption has a clear red shift compared to the solution absorption, indicating strong intermolecular interaction and aggregation.

[0099] Test Example 2, Measurement of Energy Level Using Electrochemical Cyclic Voltammetry

[0100] The oligomer prepared in Example 1 (1.0 mg) was dissolved in 1 mL of chloroform, and then the solution was added dropwise to a working electrode such as a platinum sheet; a 0.1 mol / L Bu4NPF6acetonitrile solution was used as the electrolyte; a platinum wire was used as the counter electrode; and a silver wire was used as the reference electrode. Measurement was carried out in this system using electrochemical cyclic voltammetry. The cyclic voltammetry data of the oligomer prepared in Example 1 of the present application are shown in Figure 10 . The initial oxidation potential of the oligomer of Example 1 of the present application is 0.63 V vs Ag / Ag + , and the initial reduction potential is -1.13 V vs Ag / Ag + . The HOMO energy level and LUMO energy level of 2BTR-Cl-T can be calculated by the formula (eV) and (eV) to be -5.41 eV and -3.65 eV, respectively. The above shows that the oligomeric small molecule donor compound of the present application has a suitable electronic energy level, and is suitable for use as an electron donor material in an organic solar cell.

[0101] Test Example 3: Temperature aggregation dependent absorption characteristics by variable temperature absorption test

[0102] The oligomer 2BTR-Cl-T prepared in Example 1 and BTR-Cl were dissolved in chloroform (0.01 mg / mL) respectively, and then the chloroform solutions were heated to test their variable temperature absorption spectra as shown in Figure 11 and Figure 12 Compared with the small molecule donor BTR-Cl, the absorption spectrum of the oligomer donor 2BTR-Cl-T has obvious temperature aggregation dependent characteristics, and the 0-0 / 0-1 peak ratio increases significantly with the decrease of temperature, indicating that the oligomer donor has stronger intermolecular interaction, which is conducive to realizing the phase separation of the active layer.

[0103] The structure of the small molecule donor BTR-Cl compared in the present application is as follows:

[0104]

[0105] Compared with the prior art, the beneficial effects of the present application are: the oligomeric organic small molecule donor described in the present application has better structural adjustability than the small molecule donor, and the electronic and optical properties such as energy level and band gap can be more flexibly regulated by changing the degree of polymerization. The oligomer can form a more uniform film and is not prone to diffusion when solution processed, and exhibits temperature aggregation dependent characteristics that the small molecule donor does not have in variable temperature absorption test, has stronger intermolecular interaction, reduces the risk of uneven crystallization, and improves the stability of the device. Therefore, such molecules have strong visible light absorption ability, high charge transport performance and suitable electronic energy level, and are suitable for being applied to the preparation of organic solar cells as electron donor materials.

[0106] It should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit it, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. An oligomeric small molecule donor compound, characterized in that, The oligomeric small molecule donor compound has the structure shown below:

2. The preparation method of the oligomeric small molecule donor compound according to claim 1, comprising the steps of: (1) dissolving compound 1 in ethanol, adding potassium hydroxide ethanol solution, and obtaining compound 2 through reaction; (2) dissolving compound 2 and chloroalkyl alcohol in N,N-dimethylformamide, and obtaining compound 3 through reaction; (3) dispersing compound 4, compound 5 and tetrakis(triphenylphosphine)palladium in chlorobenzene, and obtaining compound 6 through microwave reaction; (4) dissolving compound 6 in chloroform solvent, adding dehydroxyl compound 3, compound 3 and piperidine, and obtaining compound 7 through reaction; (5) dispersing compound 7, dicarboxylic acid compound, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine in chloroform, and then adding N,N'-dicyclohexylcarbodiimide, and obtaining the oligomeric small molecule donor compound through reaction; wherein Compound 1, compound 2, compound 3, compound 4, compound 5, compound 6 and compound 7 respectively have the structures shown below: The chloroalkyl alcohol is 6-chloro-1-hexanol; The dicarboxylic acid compound is 2,5-thiophenedicarboxylic acid; and the dehydroxyl compound 3 has the structure shown below:

3. The method for preparing the oligomeric small molecule donor compound according to claim 2, characterized in that, One or more of the following conditions is included: i. In step (1), the molar ratio of compound 1 to ethanol is 2-8 mol / L; the molar concentration of potassium hydroxide ethanol solution is 4-5 mol / L; the molar ratio of compound 1 to potassium hydroxide is 1:1.01-1.25; the reaction temperature is 60-100°C; the reaction time is 1-3 h; and the reaction is carried out under stirring, nitrogen or argon atmosphere; ii. In step (2), the molar ratio of compound 2 to N,N-dimethylformamide is 0.5-5 mol / L; the molar ratio of compound 2 to chloroalkyl alcohol is 1:1.0-1.5; the reaction temperature is 140-150°C; the reaction time is 2-6 h; and the reaction is carried out under reflux stirring, nitrogen or argon atmosphere; iii. In step (3), the molar ratio of compound 4, compound 5 and tetrakis(triphenylphosphine)palladium is 1:2.5-3:0.05-0.10; the molar ratio of compound 4 to chlorobenzene is 0.01-1 mol / L; the microwave reaction temperature is 150-160°C; the microwave power is 70 W; the microwave reaction time is 2-6 h; and the microwave reaction atmosphere is nitrogen or argon; iv. In step (4), the molar ratio of compound 6 to chloroform is 0.001-0.1 mol / L; the molar ratio of compound 6, dehydroxyl compound 3, compound 3 and piperidine is 1:3-4:3-4:0.001-0.15; the reaction temperature is 50-70°C; the reaction time is 10-20 h; and the reaction is carried out under stirring, nitrogen or argon atmosphere; v、In step (5), the molar ratio of the dicarboxylic acid compound, compound 7, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 1:1.8-2.2:4-4.2:0.1-0.2; the molar amount of compound 7 and the volume of chloroform are in the ratio of 0.001-0.1 mol / L; the reaction temperature after compound 7, the dicarboxylic acid compound, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine are fully dispersed in chloroform is room temperature, the reaction time is 8-12 h, and the reaction is carried out under stirring, nitrogen or argon atmosphere; the reaction temperature after N,N'-dicyclohexylcarbodiimide is added is room temperature, the reaction time is 8-12 h, and the reaction is carried out under stirring, nitrogen or argon atmosphere.

4. The application of the oligomeric small molecule donor compound as described in claim 1, characterized in that, Application of the active layer electron donor material for light capture to an organic solar cell.

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