Oligomeric small molecule donor compound as well as preparation method and application thereof

Abstract

The invention provides an oligomeric micromolecule donor compound as well as a preparation method and application thereof. The oligomeric small molecule donor compound belongs to a brand-new long conjugate organic small molecule donor material containing a connecting unit, two or more efficient organic small molecule donors are combined into a whole, the conjugate length is prolonged, and a series of novel oligomeric small molecule donor materials are synthesized. The oligomeric small molecule donor compound disclosed by the invention has good batch repeatability and relatively good film-forming property; the oligomeric small molecule donor compound prolongs the conjugate length, has excellent ultraviolet-visible light absorption performance, has strong interaction and aggregation among molecules, can realize good phase separation from a non-fullerene receptor, has a proper electron energy level, and is suitable for being used as an electron donor material in an organic solar cell.

Description

Technical Field

[0001] The invention belongs to the field of organic solar device materials, and in particular relates to an oligomeric small molecule donor compound and a preparation method and application thereof. Background Art

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

[0003] Organic solar cells generally consist of five parts: anode, anode buffer layer, active layer, cathode buffer layer and cathode. The active layer generally contains donor materials and acceptor materials. The selection of active layer materials is crucial to the efficiency of organic solar cell devices.

[0004] In recent years, the energy conversion efficiency (PCE) of organic solar cells based on conjugated polymers as donors and non-fullerene derivatives as acceptors 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 accurately control, resulting in a structure with uneven molecular weight distribution during the preparation process. This unevenness may affect electron transport, light absorption, and the crystallinity of the material, thereby affecting device performance. Chinese patent document CN115449057A discloses a conjugated polymer based on dirhodanine, which includes a dirhodanine central core and an electron-donating group, and the electron-donating end groups are connected to the two ends of the central core. The preparation process is to use tetramethylenediamine and its homologues as raw materials, cyclization reaction to obtain the dirhodanine central core, and then introduce the electron-donating structure through Knoevenagel reaction, and finally obtain the dirhodanine conjugated polymer donor material through Stille coupling. However, different batches may cause inconsistent performance due to slight differences in polymerization conditions. In addition, structural defects may occur in the polymer, such as uneven end groups, wide chain length distribution, etc., which will cause fluctuations in its photoelectric performance and affect the repeatability of the device.

[0005] In recent years, the energy conversion efficiency PCE of organic solar cells based on organic small molecules as donors and non-fullerene derivatives as acceptors has exceeded 18%. However, there are still certain defects in using organic small molecules as donor materials. Due to their short conjugation length, it is difficult to produce phase separation after blending with non-fullerene acceptors. They are greatly affected by the film preparation conditions and have 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, its preparation method and use. The compound of the invention has a wide visible absorption and a suitable energy level. The energy conversion efficiency of the solar cell prepared from the compound exceeds 8%, showing excellent photovoltaic performance. However, the molecular weight of the small molecule donor is too small and the degree of conjugation is insufficient, so it cannot be self-aggregated and precipitated preferentially, and it is easy to diffuse, resulting in difficult to control the morphology and poor stability.

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

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

[0008] The technical solution adopted by the present invention is as follows:

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

[0010]

[0011]

[0012] In formula I or II,

[0013] R1 is 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 the group consisting of a thiophenyl group, a thiophene derivative group, a dithiophenyl group, a dithiophene derivative group, a thienodithiophene derivative group, a terthiophenyl group, a terthiophene derivative group, a benzodithiophene derivative group, a pyrrolodithiophene group, a pyrrolodithiophene derivative group, a furanodithiophene group, or a furanodithiophene derivative group;

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

[0016]

[0017] Wherein, R2, R2', and R2" are independently selected from C1 to C 30 Alkyl, C1~C 30 haloalkyl, C1~C 30 Alkoxy, C1~C 30 Sulfanyl, C4~C 30 One of alkyl-substituted aryl or halogen;

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

[0019]

[0020] Among them, R3 is C1~C 30 Any one of the alkyl groups;

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

[0022]

[0023] Among them, R4 is C1~C 30 Any one of the alkyl groups.

[0024] Preferably, according to the present invention, the oligomeric small molecule donor compound has the following structure:

[0025]

[0026]

[0027] The method for preparing the above oligomeric small molecule donor compound comprises the steps of:

[0028] (1) dissolving compound 1 in ethanol, adding an ethanol solution of potassium hydroxide, and reacting to obtain compound 2;

[0029] (2) dissolving compound 2 and chloroalkyl alcohol in N'N-dimethylformamide to obtain compound 3 through reaction;

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

[0031] (4) Compound 6 is dissolved in chloroform solvent, and dehydroxylated compound 3, compound 3 and piperidine are added to obtain compound 7 through reaction;

[0032] (5) Compound 7, a dicarboxylic acid compound, N,N'-dicyclohexylcarboximide and 4-dimethylaminopyridine are fully dispersed in chloroform to react; then N,N'-dicyclohexylcarboximide is added to react to obtain an oligomeric small molecule donor compound.

[0033] Wherein, compound 1 is selected from one of the following compounds:

[0034]

[0035] In chloroalkyl alcohol, the alkyl group is C1~C 30 The 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 derivatives, dithiophene, dithiophene derivatives, thienodithiophene derivatives, terthiophene, terthiophene derivatives, benzodithiophene derivatives, pyrrolodithiophene, pyrrolodithiophene derivatives, furanodithiophene or furanodithiophene derivatives;

[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, and 1,2-phenyl dicarboxylic acid.

[0039] According to the preferred embodiment of the present invention, 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 preferred embodiment of the present invention, the chloroalkyl alcohol is 6-chloro-1-hexanol; the dicarboxylic acid compound is 2,5-thiophenedicarboxylic acid; and the dehydroxylated compound 3 has the following structure:

[0043]

[0044] Preferably, in step (1), the volume ratio of the molar amount of compound 1 to ethanol is 2-8 mol / L; the molar concentration of the ethanol solution of potassium hydroxide 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 1-3h, and the reaction is carried out under stirring conditions in a nitrogen or argon atmosphere.

[0045] Preferably, in step (1), the post-treatment method of the reaction solution obtained by the reaction is as follows: washing the reaction solution with cold ethanol and drying to obtain compound 2.

[0046] Preferably, according to the present invention, in step (2), the volume ratio of the molar amount of compound 2 and N'N-dimethylformamide is 0.5-5 mol / L: the molar ratio of compound 2 and chloroalkyl alcohol is 1:1.0-1.5: the reaction temperature is 140-150°C, the reaction time is 2-6h, and the reaction is carried out in a nitrogen or argon atmosphere under reflux stirring conditions.

[0047] Preferably, in step (2), the post-treatment method of the reaction solution obtained by the reaction is as follows: the reaction solution is extracted with ethyl acetate, the organic phase is taken, and the solvent is dried to obtain a crude product; and then the crude product is separated by column chromatography to obtain compound 3.

[0048] Preferably according to the present invention, 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 volume ratio of the molar amount of compound 4 and chlorobenzene is 0.01-1 mol / L; the microwave reaction temperature is 150-160°C, the microwave power is 70W, the microwave reaction time is 2-6h, and the microwave reaction atmosphere is nitrogen or argon.

[0049] Preferably, in step (3), the post-treatment method of the reaction solution obtained by the reaction is as follows: the reaction solution is extracted with dichloromethane, the organic phase is taken, the solvent is spin-dried, and then the compound 6 is obtained by column chromatography separation.

[0050] Preferably according to the present invention, in step (4), the volume ratio of the molar amount 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°C, the reaction time is 10-20h, and the reaction is carried out under stirring in a nitrogen or argon atmosphere.

[0051] Preferably, in step (4), the post-treatment method of the reaction solution obtained by the reaction is as follows: the reaction solution 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 separated by column chromatography to obtain compound 7.

[0052] Preferably, according to the present invention, in step (5), the molar ratio of the dicarboxylic acid compound, compound 7, N,N'-dicyclohexylcarboximide and 4-dimethylaminopyridine is 1:1.8-2.2:4-4.2:0.1-0.2; the volume ratio of the molar amount of compound 7 to chloroform is 0.001-0.1 mol / L; the reaction temperature after fully dispersing compound 7, dicarboxylic acid compound, N,N'-dicyclohexylcarboximide and 4-dimethylaminopyridine in chloroform is room temperature, the reaction time is 8-12h, and the reaction is carried out under stirring in a nitrogen or argon atmosphere; the reaction temperature after adding N,N'-dicyclohexylcarboximide is room temperature, the reaction time is 8-12h, and the reaction is carried out under stirring in a nitrogen or argon atmosphere.

[0053] Preferably, in step (5) of the present invention, the post-treatment method of the reaction solution obtained by the reaction is as follows: the reaction solution 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 separated by column chromatography to obtain the oligomeric small molecule donor compound.

[0054] The above oligomeric small molecule donor compound is used as an active layer electron donor material for light harvesting in organic solar cells.

[0055] The technical features and beneficial effects of the present invention are as follows:

[0056] 1. The oligomeric small molecule donor compound of the present invention can be prepared by a solution method, has a simple structure, is easy to synthesize, has a high yield, and has good batch repeatability; it can be dissolved in organic solvents such as chloroform, tetrahydrofuran and chlorobenzene, and has good film-forming properties.

[0057] 2. The novel oligomeric small molecule donor compound provided by the present invention belongs to a new class of long conjugated organic small molecule donor materials containing connecting units. It combines two high-efficiency organic small molecule donors into one, extends the conjugation length, and synthesizes a series of novel oligomeric small molecule donor materials. The oligomeric small molecule donor compound of the present invention has the main skeleton structure of the star small molecule donor, so that it has excellent ultraviolet-visible light absorption performance, has strong absorption in the range of 400-700nm, and the thin film absorption has an obvious absorption red shift compared to the solution absorption, indicating that there are strong interactions and aggregation between molecules. The oligomeric small molecule donor compound of the present invention has a suitable electronic energy level and is suitable for use as an electron donor material in an organic solar cell. At the same time, the introduction of the connecting unit of the present invention 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, thereby improving the stability of the active layer of the all-small molecule solar cell and effectively improving the mechanical strength of the battery.

[0058] 3. Compared with small molecules and polymers, the oligomers of the present invention have better structural controllability, film-forming properties, and flexibility in performance regulation. Compared with polymers, the molecular weight of oligomers is easier to control, the crystallinity is better, the film is more uniform when formed, and the device performance is more stable; compared with small molecules, oligomers have a moderate molecular weight, which not only maintains good solubility and tensile properties, but also can achieve energy level and photoelectric performance regulation by adjusting the degree of polymerization. In addition, the environmental stability and device repeatability of oligomers are better than those of small molecules, thus showing better comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 The compound 3 prepared in Example 1 of the present invention 1 H NMR.

[0060] Figure 2 The compound 3 prepared in Example 1 of the present invention 13 C NMR.

[0061] Figure 3 The compound 6 prepared in Example 1 of the present invention 1 H NMR.

[0062] Figure 4 The compound 6 prepared in Example 1 of the present invention 13 C NMR.

[0063] Figure 5 The compound 7 prepared in Example 1 of the present invention 1 H NMR.

[0064] Figure 6 The compound 7 prepared in Example 1 of the present invention 13C NMR.

[0065] Figure 7 The novel oligomeric organic small molecule donor 2BTR-Cl-T prepared in Example 1 of the present invention 1 HNMR.

[0066] Figure 8 This is the mass spectrum of the novel oligomeric organic small molecule donor 2BTR-Cl-T prepared in Example 1 of the present invention.

[0067] Fig. 9 This is a UV-visible absorption spectrum of the novel oligomeric organic small molecule donor 2BTR-Cl-T prepared in Example 1 of the present invention in a chloroform solution and in a thin film state;

[0068] Fig.10 This is a cyclic voltammetry curve of the novel oligomeric organic small molecule donor 2BTR-Cl-T prepared in Example 1 of the present invention;

[0069] Fig.11 This is a temperature-dependent UV-visible absorption spectrum of the novel oligomeric organic small molecule donor 2BTR-Cl-T prepared in Example 1 of the present invention;

[0070] Fig.12 The temperature-dependent UV-visible absorption spectrum of the organic small molecule donor BTR-Cl;

[0071] Fig.13 This is a synthetic route for the novel oligomeric organic small molecule donor 2BTR-Cl-T prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0072] In order to make the purpose, technical solution and effect of the present application clearer and more specific, 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 are not used to limit the present application.

[0073] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, the technical solutions of the present invention are further described below in conjunction with the accompanying drawings and embodiments. However, the present invention is not limited to the embodiments listed, and should also include any other known changes within the scope of the rights claimed by the present invention.

[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] Synthesis route such as Fig.13 As shown, the specific preparation method is as follows:

[0078] Step 1) synthesizing compound 2;

[0079] Under nitrogen atmosphere, compound 1 (5.1 g, 38.1 mmol) was dissolved in 9 mL of ethanol solution. At 80 °C, 9 mL of ethanol solution containing potassium hydroxide (2.2 g, 40.0 mmol) was slowly added. After stirring for 2 hours, the reaction solution was washed twice with cold ethanol and air-dried. The obtained compound 2 was directly used for the next step reaction.

[0080] Step 2) synthesizing compound 3;

[0081] The crude product compound 2 (990 mg, 5.8 mmol) obtained in the previous step and 6-chloro-1-hexanol (868 mg, 6.4 mmol) were dissolved in 5 mL of N'N-dimethylformamide and refluxed with stirring at 145°C in a nitrogen atmosphere for 4 hours. The mixture was extracted with ethyl acetate, the organic phase was taken, and the solvent was dried by spin drying. The crude product was separated by column chromatography using petroleum ether / ethyl acetate (volume ratio 2:1) as an eluent to obtain compound 3 (300 mg, yield 25%).

[0082] The NMR spectrum of compound 3 is as follows Figure 1 and Figure 2 The structural confirmation data are as follows: 1 H NMR (400MHz, CDCl3) δ4.01-3.95 (m, 4H), 3.68-3.60 (t, J = 6.5Hz, 2H), 1.71-1.61 (m, 2H), 1.61-1.53 ​​(m, 2H), 1.47-1.37 (m, 4H). 13 C NMR (101MHz, CDCl3) δ201.24,173.93,62.76,44.63,35.36,32.51,26.64,26.48,25.23.

[0083] Step 3) synthesizing 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, nitrogen was replaced three times, microwave power was 70 W, and microwave reaction was performed at 155°C for 4 hours. After the reaction was completed, dichloromethane was extracted, the organic phase was taken, the solvent was dried, and the crude product was separated by column chromatography using petroleum ether / dichloromethane (volume ratio 1:2) as an eluent to finally obtain compound 6 (235 mg, yield 71%).

[0085] The NMR spectrum of compound 6 is as follows Figure 3 and Figure 4 The structural confirmation data are as follows: 1 H NMR (400MHz, CDCl3) δ9.90-9.87(d,J=1.0Hz,2H),7.72-7.69(dd,J=4.0,1.6Hz,2H),7.59-7.31(d,J=77.2Hz,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=4.3Hz,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 (101MHz, CDCl3) δ182.57,146.01,142.58,142.25,141.23,138.72,138 .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) synthesizing 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. The reaction mixture was then stirred at 60 ° C for 12 hours in an argon atmosphere protected by argon. After stirring and reacting for 12 hours, the reaction mixture was extracted three times with chloroform. The organic layer was washed three times with water and then dried with anhydrous magnesium sulfate. After removing 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 silica gel method. The column chromatography eluent was chloroform: methanol = 98:2 (volume ratio), and the product compound 7 (106 mg, yield 35.6%) was finally obtained.

[0088] The NMR spectrum of compound 7 is as follows Figure 5 and Figure 6 The structural confirmation data are as follows: 1H NMR (400MHz, CDCl3) δ7.75-7.69(s,2H),7.43-7.34(s,2H),7.29-7.19(d,J=9.5Hz,4H),7.13 -7.05(d,J=4.0Hz,2H),7.01-6.94(s,2H),6.93-6.86(d,J=3.6Hz,2H),4.11-3.97(dt,J=10.4 ,5.3Hz,4H),3.66-3.61(t,J=6.5Hz,2H),2.97-2.88(m,4H),2.78-2.71(t,J=7.9Hz,4H),2.7 1-2.63(t,J=8.1Hz,4H),1.85-1.77(q,J=6.3Hz,2H),1.70-1.64(m,12H),1.43-0.86(m,77H). 13 C NMR (101MHz, CDCl3) δ192.05,167.41,144.33,141.84,140.82,138.49,138.43,137.78,137 .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) synthesizing compound 2BTR-Cl-T;

[0090] Compound 7 (50 mg, 0.025 mmol), 2,5-thiophenedicarboxylic acid (2.21 mg, 0.013 mmol), N,N'-dicyclohexylcarboximide (5.30 mg, 0.027 mmol) and 4-dimethylaminopyridine (0.31 mg, 0.002 mmol) were mixed, and 12 mL of chloroform was added. The reaction mixture was then stirred at room temperature for 10 hours in an inert atmosphere protected by argon. N,N'-dicyclohexylcarboximide (5.30 mg, 0.027 mmol) was added and stirred at room temperature for 10 hours in an inert atmosphere protected by argon. The reaction mixture was extracted three times with chloroform. The organic layer was washed three times with water and dried with anhydrous magnesium sulfate. After removing 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. The column chromatography eluent was petroleum ether: chloroform = 1:2 (volume ratio), and finally the product compound 2BTR-Cl-T (8 mg, yield 14%) was obtained.

[0091] The NMR spectrum of compound 2BTR-Cl-T is as follows Figure 7 As shown, the mass spectrum Figure 8 The structural confirmation data are as follows: 1 HNMR(400MHz, CDCl3)δ7.76-7.74(s,2H),7.74-7.66(m,4H),7.35-7.32(t,J=4.0Hz, 4H),7.29-7.19(s,8H),7.14-6.82(m,12H),4.31-4.25(t,J=5.0Hz,4H),4.08-4.00(d ,J=11.2Hz,10H),2.95-2.89(m,8H),2.76-2.61(dd,J=28.4,7.9Hz,16H),2.25-2.19( t,J=7.6Hz,8H),2.10-1.92(d,J=6.2Hz,16H),1.86-0.68(m,160H).MS(MALDI-TOF)of 2BTR-Cl-T m / z:[M+H]+calcd for C 210 H 253 Cl4N4O8S 29 ,4032.016,found:4032.435.

[0092] The NMR spectrum and mass spectrum of compound 2BTP-Cl-T show that compound 2BTP-Cl-T is an oligomeric small molecule donor compound as described above.

[0093] Experimental Example 1. Processability of the oligomer of the present invention and measurement of the optical band gap using absorption spectroscopy

[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 film with a thickness of 78 nm was prepared by spin coating a chloroform solution of the oligomer at a concentration of 10 mg / mL onto a glass slide.

[0095] The absorption spectra of the oligomer prepared in Example 1 in chloroform solution (concentration 0.01 mg / mL) and in the film state are shown in Fig. 9 The optical band gap of the polymer is calculated using the empirical formula (E g opt =1240 / λ absorption onset, where: E g opt is the optical band gap of the polymer; λ absorption onset is the starting point of the absorption spectrum in the long-wave direction) and are calculated and shown in Table 1.

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

[0097]

[0098] like Fig. 9 As shown, there is strong absorption in the range of 400-700 nm, and the film absorption has an obvious red shift compared to the solution absorption, indicating that there are strong interactions and aggregations between molecules.

[0099] Experimental Example 2: Energy Level Measurement 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 dripped onto a working electrode such as a platinum sheet; a 0.1 mol / L Bu4NPF6 acetonitrile solution was used as an electrolyte; a platinum wire was used as a counter electrode; and a silver wire was used as a reference electrode. Electrochemical cyclic voltammetry measurements were performed in this system. The cyclic voltammetry data of the oligomer prepared in Example 1 of the present invention are shown in Fig.10 Example 1 of the present invention, the initial oxidation potential of the oligomer 0.63V vsAg / Ag + , initial reduction potential Yes -1.13V vs Ag / Ag + By formula (eV) and (eV) It can be calculated that the HOMO energy level and LUMO energy level of 2BTR-Cl-T are -5.41eV and -3.65eV respectively. The above shows that the oligomeric small molecule donor compound of the present invention has a suitable electron 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 Temperature Variable Absorption Test

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

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

[0104]

[0105] Compared with the prior art, the beneficial effects of the present invention are as follows: the oligomeric organic small molecule donors described in the present invention have better structural adjustability than small molecule donors, and electronic and optical properties, such as energy levels and band gaps, can be more flexibly regulated by changing the degree of polymerization. Oligomers can form more uniform films and are not easy to diffuse during solution processing. The variable temperature absorption test shows temperature aggregation dependence characteristics that small molecule donors do not have. They have stronger intermolecular interactions, reduce the risk of uneven crystallization, and improve the stability of the device. Therefore, this type of molecule has strong visible light absorption ability, high charge transfer performance and suitable electronic energy levels, and is suitable for use as electron donor materials in the preparation of organic solar cells.

[0106] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention 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 invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An oligomeric small molecule donor compound, characterized in that: Having a structure as shown in Formula I or II: In formula I or II, R1 is 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; Ar is selected from the group consisting of a thiophenyl group, a thiophene derivative group, a dithiophenyl group, a dithiophene derivative group, a thienodithiophene derivative group, a terthiophenyl group, a terthiophene derivative group, a benzodithiophene derivative group, a pyrrolodithiophene group, a pyrrolodithiophene derivative group, a furanodithiophene group, or a furanodithiophene derivative group; EG is selected from any one of the following structures: Wherein, R2, R2', and R2" are independently selected from C1 to C 30 Alkyl, C1~C 30 haloalkyl, C1~C 30 Alkoxy, C1~C 30 Sulfanyl, C4~C 30 One of alkyl-substituted aryl or halogen; The electron withdrawing group A1 is selected from one of the following structures: Among them, R3 is C1~C 30 Any one of the alkyl groups; The electron withdrawing group A2 is selected from one of the following structures: Among them, R4 is C1~C 30 Any one of the alkyl groups.

2. The oligomeric small molecule donor compound according to claim 1, characterized in that: The oligomeric small molecule donor compound has the structure shown below:

3. The method for preparing the oligomeric small molecule donor compound according to claim 1 or 2, comprising the steps of: (1) dissolving compound 1 in ethanol, adding an ethanol solution of potassium hydroxide, and reacting to obtain compound 2; (2) dissolving compound 2 and chloroalkyl alcohol in N'N-dimethylformamide to obtain compound 3 through reaction; (3) Compound 4, compound 5 and tetrakis(triphenylphosphine)palladium are fully dispersed in chlorobenzene, and compound 6 is obtained by microwave reaction; (4) Compound 6 is dissolved in chloroform solvent, and dehydroxylated compound 3, compound 3 and piperidine are added to obtain compound 7 through reaction; (5) Compound 7, a dicarboxylic acid compound, N,N'-dicyclohexylcarboximide and 4-dimethylaminopyridine are fully dispersed in chloroform to react; then N,N'-dicyclohexylcarboximide is added to react to obtain an oligomeric small molecule donor compound; in, Compound 1 is selected from one of the following compounds: In chloroalkyl alcohol, the alkyl group is C1~C 30 The alkyl group; Compound 4 is (CH3)3Sn-EG-Sn(CH3)3, wherein EG is the same as EG in formula I or II; Compound 5 is one of thiophene, thiophene derivatives, dithiophene, dithiophene derivatives, thienodithiophene derivatives, terthiophene, terthiophene derivatives, benzodithiophene derivatives, pyrrolodithiophene, pyrrolodithiophene derivatives, furanodithiophene or furanodithiophene derivatives; 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, and 1,2-phenyl dicarboxylic acid.

4. The method for preparing the oligomeric small molecule donor compound according to claim 3, characterized in that: Compound 1, Compound 2, Compound 3, Compound 4, Compound 5, Compound 6, and Compound 7 have the following structures respectively:

5. The method for preparing the oligomeric small molecule donor compound according to claim 3, characterized in that: The chloroalkyl alcohol is 6-chloro-1-hexanol; the dicarboxylic acid compound is 2,5-thiophenedicarboxylic acid; and the dehydroxylated compound 3 has the following structure:

6. The method for preparing the oligomeric small molecule donor compound according to claim 3, characterized in that: Includes one or more of the following conditions: i. In step (1), the volume ratio of the molar amount of compound 1 to ethanol is 2-8 mol / L; the molar concentration of the ethanol solution of potassium hydroxide 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 1-3h, and the reaction is carried out under stirring conditions in a nitrogen or argon atmosphere; ii. In step (2), the volume ratio of the molar amount of compound 2 and N'N-dimethylformamide is 0.5-5 mol / L: the molar ratio of compound 2 and chloroalkyl alcohol is 1:1.0-1.5: the reaction temperature is 140-150°C, the reaction time is 2-6h, and the reaction is carried out in a nitrogen or argon atmosphere under reflux stirring conditions; 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 volume ratio of the molar amount of compound 4 and chlorobenzene is 0.01-1 mol / L; the microwave reaction temperature is 150-160°C, the microwave power is 70W, the microwave reaction time is 2-6h, and the microwave reaction atmosphere is nitrogen or argon; iv. In step (4), the volume ratio of the molar amount 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°C, the reaction time is 10-20h, and the reaction is carried out under stirring in a nitrogen or argon atmosphere; v. In step (5), the molar ratio of the dicarboxylic acid compound, compound 7, N,N'-dicyclohexylcarboximide and 4-dimethylaminopyridine is 1:1.8-2.2:4-4.2:0.1-0.2; the volume ratio of the molar amount of compound 7 to chloroform is 0.001-0.1 mol / L; the reaction temperature after fully dispersing compound 7, dicarboxylic acid compound, N,N'-dicyclohexylcarboximide and 4-dimethylaminopyridine in chloroform is room temperature, the reaction time is 8-12h, and the reaction is carried out under stirring in a nitrogen or argon atmosphere; the reaction temperature after adding N,N'-dicyclohexylcarboximide is room temperature, the reaction time is 8-12h, and the reaction is carried out under stirring in a nitrogen or argon atmosphere.

7. The use of the oligomeric small molecule donor compound as claimed in claim 1 or 2, characterized in that: It is used as an active layer electron donor material for light harvesting in organic solar cells.

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