Asymmetric donor material with different fluorine contents as well as preparation method and application of asymmetric donor material

Abstract

The invention relates to the technical field of organic photoelectric materials, in particular to asymmetric donor materials with different fluorine contents as well as a preparation method and application of the asymmetric donor materials, and discloses organic small molecule donor materials with different fluorine atom-containing asymmetric two-dimensional side chains, Z-2F for short, the structural formula of the organic small molecule donor materials is shown as a formula 1, and a preparation method of the donor materials. The application of the donor material in preparation of functional energy devices including solar cells, organic light-emitting diodes and flexible displays, including application in the field of water surface photovoltaics, the designed fluorine atom-containing micromolecule donor material and the acceptor material L8-BO form a proper energy level difference, and the functional energy devices can be applied to the field of water surface photovoltaics. Therefore, exciton dissociation is facilitated, and better photovoltaic performance and wider water surface photovoltaic application are achieved in organic solar cell testing.

Description

Technical Field

[0001] The invention relates to the technical field of organic photoelectric materials, in particular to an asymmetric donor material with different fluorine contents and a preparation method and application thereof. Background Art

[0002] When designing organic optoelectronic materials, halogen atoms such as fluorine (F) and chlorine (Cl) play an important role in improving material performance and expanding their functions due to their unique electronic properties: such as increasing material stability and improving charge transport capabilities, regulating optical absorption and emission properties, etc.

[0003] As a supplement to silicon solar cells, organic solar cells have great application potential in water surface photovoltaics, indoor photovoltaics, photovoltaic agriculture, photovoltaic new energy vehicles, etc. By introducing asymmetric side chains into all-small molecule donors, a highly efficient small molecule donor Z-2F was obtained, and by adding fluorine atoms to the benzene ring, the structure of the compound was fine-tuned, the HOMO energy level was reduced, the interaction between molecules was increased, and the donor and acceptor were better miscible. The maximum efficiency of the device is as high as 17.9%, which is one of the highest values ​​of the efficiency of organic solar devices floating on the water surface.

[0004] Therefore, when developing new organic optoelectronic materials, it is a common strategy to rationally select and introduce fluorine or chlorine atoms to optimize the optoelectronic properties of the materials and meet the needs of specific applications. However, the introduction of fluorine atoms also has its challenges, such as increased synthesis difficulty, increased costs, and environmental friendliness issues. At the same time, the environmental impact and sustainability issues that may be caused by the introduction of halogens should also be considered. Summary of the invention

[0005] The purpose of the present application is to provide an asymmetric donor material with different fluorine contents and a preparation method and application thereof, so that it has better photovoltaic performance and wider surface photovoltaic applications.

[0006] The present application provides an asymmetric donor material with different fluorine contents, specifically an organic small molecule donor material with asymmetric two-dimensional side chains containing different fluorine atoms, and its structural formula is shown in Formula 1:

[0007]

[0008] Furthermore, the preparation method of the asymmetric donor material with different fluorine contents specifically comprises the following steps:

[0009] S1: Using tetrahydrofuran as solvent and iodine as initiator, magnesium powder and 4-bromo-1,2-difluorobenzene are added, and the mixture is refluxed at 70°C for 4h to perform reflux reaction until magnesium is completely consumed, and then naturally cooled to room temperature to obtain Grignard reagent 1. Grignard reagent 1 is added dropwise to a toluene solution of benzo[1,2-b:4,5-b']dithiophene-4,8-dione, and stirred at room temperature. At the same time, using tetrahydrofuran as solvent and iodine as initiator, magnesium powder, 5-bromo-3-chloro-2-(2-hexyldiethyl)thiocin, and The mixture was refluxed at 70°C for 2h until magnesium was completely consumed, and naturally cooled to room temperature to obtain Grignard reagent 2, and then the newly prepared Grignard reagent 2 was transferred to a dropping funnel and slowly dripped into the mixed solution to which Grignard reagent 1 was added. Subsequently, the mixture was stirred at room temperature overnight, and then dihydrate tin (II) chloride dissolved in 10% HCl was added at room temperature, and then the resulting solution was stirred at 50°C for 3 hours; after completion, the reaction was naturally cooled to room temperature and poured into water to obtain compound 1;

[0010] S2: under the protection of argon, n-butyl lithium solution was added dropwise to the tetrahydrofuran solution containing compound 1 at -78°C. After the addition, the mixture was stirred at -78°C for 1 hour, and then compound 1 was added. The mixture was continuously stirred at -78°C for 1 hour, and the temperature was naturally raised to room temperature for reaction for 12 hours. Subsequently, the mixture was cooled to room temperature, and a tin reagent solution was added; then the mixture was stirred at 50°C for another 3 hours to generate compound 2; the tin reagent solution was prepared by dissolving tin (II) chloride dihydrate in 10% HCl;

[0011] S3: Under argon protection, using tetrakis(triphenylphosphine)palladium as a catalyst and toluene as a solvent, compound 2 and 5"-bromo-3',3"-dihexyl-[2,2':5',2"-terthiophene]-5-carbaldehyde were refluxed at 110°C for 8 to 10 hours to produce a Stille coupling reaction to obtain compound 3;

[0012] S4: Under argon protection, compound 3, 3-hexylrhodanine and a base were added to the solvent chloroform, and a Knoevenagel condensation reaction was carried out at 60°C to connect the rhodanine end groups to obtain an organic small molecule donor material containing an asymmetric two-dimensional side chain, referred to as compound Z-2F.

[0013] Furthermore, the molar ratio of 5-bromo-3-chloro-2-(2-hexyldiethyl) thiocine, 4-bromo-1,2-difluorobenzene and benzo[1,2-b:4,5-b']dithiophene-4,8-dione in S1 is 1:2:2.3, and the molar ratio of benzo[1,2-b:4,5-b']dithiophene-4,8-dione to tin reagent is 1:5.

[0014] Furthermore, the molar ratio of compound 1 to the tin reagent in S2 is 1:2.5; the molar ratio of n-butyl lithium to compound 1 is 1:3.5.

[0015] Furthermore, the optimal conditions for the reflux reaction in S3 are reflux reaction at 110° C. for 9 hours; the molar ratio of compound 2 to 5”-bromo-3',3”-dihexyl-[2,2':5',2”-terthiophene]-5-carbaldehyde in S3 is 1:15, and the molar ratio of the catalyst to compound 3 is 20 mg:10.31 mmol.

[0016] Furthermore, the reaction time of the condensation reaction in S4 is 24 h; the molar ratio of 3-hexylrhodanine to compound 3 in S4 is 15:1; and the molar ratio of the base to compound 3 is 1.5 mL:0.654 mmol.

[0017] Furthermore, asymmetric donor materials with different fluorine contents are used in the preparation of the following functional energy devices: solar cells, organic light-emitting diodes and flexible displays.

[0018] Furthermore, the solar cell comprises a water-surface floating organic solar cell; the water-surface floating organic solar cell comprises a solar panel made of Z-2F material and a water-surface floating structure.

[0019] The beneficial effects of the present invention are as follows: the present invention simultaneously introduces a benzene ring and thiophene into a small molecule donor material, utilizes an asymmetric two-dimensional side chain to design and synthesize a completely new small molecule donor material, and achieves a photoelectric conversion efficiency of 17.9%, which has important application prospects in binary all-small molecule organic solar cells and provides a certain theoretical basis for ternary organic solar cells; the fluorine-containing small molecule donor material designed by the present invention forms an appropriate energy level difference with the acceptor material L8-BO, which is beneficial to exciton dissociation, and has better photovoltaic performance and a wider range of surface photovoltaic applications in the test of organic solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Compound 1 prepared by the present invention 1 H NMR spectrum.

[0021] Figure 2 Compound 1 prepared by the present invention 13 C NMR spectrum.

[0022] Figure 3 Compound 2 prepared by the present invention 1 H NMR spectrum.

[0023] Figure 4 Compound 2 prepared by the present invention13 C NMR spectrum.

[0024] Figure 5 The compound Z-2F prepared by the present invention is 1 H NMR spectrum.

[0025] Figure 6 The compound Z-2F prepared by the present invention is 13 C NMR spectrum.

[0026] Figure 7 The normalized UV-visible absorption spectra of the compound Z-2F film, Z-2F solution and L8-BO film prepared in the present invention.

[0027] Figure 8 The cyclic voltammetry curves of the compounds Z-2F, L8-BO and Ferrocene prepared in the present invention are shown.

[0028] Fig. 9 Schematic diagram of the structure of the water surface floating system.

[0029] Fig.10 1 is a flow chart of the reaction compounds in each step of Example 1.

[0030] In the figure:

[0031] 1. Floating structure; 2. PV panels; 3. Fixed bracket; 4. Hinge structure. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] An asymmetric donor material with different fluorine contents, specifically an organic small molecule donor material with an asymmetric two-dimensional side chain containing different fluorine atoms, and its structural formula is shown in Formula 1:

[0034]

[0035] The method for preparing the above-mentioned asymmetric donor materials with different fluorine contents specifically comprises the following steps:

[0036] S1: Using tetrahydrofuran as solvent and iodine as initiator, magnesium powder and 4-bromo-1,2-difluorobenzene are added, and the mixture is refluxed at 70°C for 4h to perform reflux reaction until magnesium is completely consumed, and then naturally cooled to room temperature to obtain Grignard reagent 1. Grignard reagent 1 is added dropwise to a toluene solution of benzo[1,2-b:4,5-b']dithiophene-4,8-dione, and stirred at room temperature. At the same time, using tetrahydrofuran as solvent and iodine as initiator, magnesium powder, 5-bromo-3-chloro-2-(2-hexyldiethyl)thiocin, and The mixture was refluxed at 70°C for 2h until magnesium was completely consumed, and naturally cooled to room temperature to obtain Grignard reagent 2, and then the newly prepared Grignard reagent 2 was transferred to a dropping funnel and slowly dripped into the mixed solution to which Grignard reagent 1 was added. Subsequently, the mixture was stirred at room temperature overnight, and then dihydrate tin (II) chloride dissolved in 10% HCl was added at room temperature, and then the resulting solution was stirred at 50°C for 3 hours; after completion, the reaction was naturally cooled to room temperature and poured into water to obtain compound 1;

[0037] S2: under the protection of argon, n-butyl lithium solution was added dropwise to the tetrahydrofuran solution containing compound 1 at -78°C. After the addition, the mixture was stirred at -78°C for 1 hour, and then compound 1 was added. The mixture was continuously stirred at -78°C for 1 hour, and the temperature was naturally raised to room temperature for reaction for 12 hours. Subsequently, the mixture was cooled to room temperature, and a tin reagent solution was added; then the mixture was stirred at 50°C for another 3 hours to generate compound 2; the tin reagent solution was prepared by dissolving tin (II) chloride dihydrate in 10% HCl;

[0038] S3: Under argon protection, using tetrakis(triphenylphosphine)palladium as a catalyst and toluene as a solvent, compound 2 and 5"-bromo-3',3"-dihexyl-[2,2':5',2"-terthiophene]-5-carbaldehyde were refluxed at 110°C for 8 to 10 hours to produce a Stille coupling reaction to obtain compound 3;

[0039] S4: Under argon protection, compound 3, 3-hexylrhodanine and a base are added to chloroform solvent, wherein the base is preferably piperidine, and a Knoevenagel condensation reaction is carried out at 60°C to connect the rhodanine end groups to obtain an organic small molecule donor material containing an asymmetric two-dimensional side chain, referred to as compound Z-2F.

[0040] The molar ratio of the three substances of 5-bromo-3-chloro-2-(2-hexyldiethyl) thiocine, 4-bromo-1,2-difluorobenzene and benzo[1,2-b:4,5-b']dithiophene-4,8-dione in S1 is 1:2:2.3, and the molar ratio of the benzo[1,2-b:4,5-b']dithiophene-4,8-dione to the tin reagent is 1:5.

[0041] The molar ratio of compound 1 to the tin reagent in S2 is 1:2.5; the molar ratio of n-butyl lithium to compound 1 is 1:3.5.

[0042] The optimal conditions for the reflux reaction in S3 are reflux reaction at 110° C. for 9 hours; the molar ratio of compound 2 to 5”-bromo-3',3”-dihexyl-[2,2':5',2”-terthiophene]-5-carbaldehyde in S3 is 1:15, and the molar ratio of the catalyst to compound 3 is 20 mg:10.31 mmol.

[0043] The reaction time of the condensation reaction in S4 is 24 h; the molar ratio of 3-hexylrhodanine to compound 3 in S4 is 15:1; and the molar ratio of the base to compound 3 is 1.5 mL:0.654 mmol.

[0044] Example 1: Synthesis of compound Z-2F, the process is as follows Fig.10 shown.

[0045] (1) Synthesis of Compound 1:

[0046] 4-Bromo-1,2-difluorobenzene (52.11 mmol) and magnesium powder (62.53 mmol) were added to a round-bottom flask filled with redistilled tetrahydrofuran (50 mL). Subsequently, iodine (20 mg) was added to the round-bottom flask as an initiator. The mixture was refluxed at 70 ° C for 4 h until the magnesium was completely consumed. After the reaction was naturally cooled to room temperature (25 ° C, the same below), Grignard reagent 1 was obtained. The newly prepared Grignard reagent 1 was then transferred to a dropping funnel and slowly dripped (30 drops per minute) into a toluene solution of 150 mL containing benzo[1,2-b:4,5-b′]dithiophene-4,8-dione (46.51 mmol). Subsequently, 5-bromo-3-chloro-2-(2-hexyldiethyl)thiocine (23.91 mmol) and magnesium powder (28.69 mmol) were added to a round-bottom flask filled with redistilled tetrahydrofuran (50 mL). Subsequently, iodine (20 mg) was added to the round-bottom flask as an initiator. The mixture was refluxed at 70°C for 2 h until magnesium was completely consumed. After the reaction was naturally cooled to room temperature (25°C, the same below), Grignard reagent 2 was obtained, and then the newly prepared Grignard reagent 2 was transferred to a dropping funnel and slowly dripped into the above mixed solution (30 drops per minute). Subsequently, the mixture was stirred at room temperature overnight, and then dihydrated tin (II) chloride (260.55 mmol) dissolved in 10% HCl (15 mL) was added, and the resulting solution was stirred at 50°C for 3 hours. After completion, the reaction mixture was naturally cooled to room temperature and poured into water. The obtained organic phase was extracted three times with dichloromethane and then dried over anhydrous sodium sulfate. After the solvent was removed by a rotary evaporator, the crude product was purified by silica gel column chromatography (eluent: petroleum ether) to obtain a pale white solid - Compound 1 (yield 63%), i.e. 4-(4-chloro-5-(2-hexyldecyl)thiophen-2-yl)-8-(3,4-difluorophenyl)benzo[1,2-b:4,5-b']dithiophene, which 1 HNMR spectrum see Figure 1 .

[0047] (2) Synthesis of Compound 2

[0048] Under argon protection and at -78°C, n-butyl lithium (54.53 mmol, 1.6 M) was added dropwise (30 drops per minute) to a tetrahydrofuran solution (60 mL) of compound 1 (15.58 mmol). After the addition, the mixture was stirred at -78°C for 1 h. Then a tetrahydrofuran solution of trimethyltin chloride (38.95 mmol, 1 M) was added and stirred again at -78°C for 1 h, then the mixture was naturally warmed to room temperature. After stirring at room temperature for 12 h, the solution was poured into deionized water, extracted three times with anhydrous ether (50 mL each time), and then dried over anhydrous sodium sulfate. After removing the solvent with a rotary evaporator, the crude product was recrystallized in toluene (the operating steps of recrystallization are: add 50 ml of toluene to the crude product, heat to 55-60°C to dissolve the product, turn off the heating after dissolution, cool naturally to room temperature, and leave for 5 hours, filter the precipitated crystalline product, the same below) twice to obtain a yellow solid compound 2 (the yield of this step is 80%). 1 HNMR Figure 2 .

[0049] (3) Synthesis of Compound 3

[0050] Under argon protection, compound 2 (10.31 mmol), 5"-bromo-3',3"-dihexyl-[2,2':5',2"-trithiophene]-5-carboxaldehyde (154.65 mmol) and tetrakis(triphenylphosphine)palladium (20 mg) were added to a round-bottom flask, and then anhydrous toluene (30 mL) was added thereto, and the mixture was stirred at 110°C for 9 h. After naturally cooling to room temperature, it was quenched with deionized water, and the resulting organic matter was extracted with dichloromethane 3 times (50 mL each time), and then dried over anhydrous sodium sulfate. After removing the solvent with a rotary evaporator, the crude product was purified by silica gel column chromatography (eluent: dichloromethane) to obtain a red solid compound 3 (yield of this step 48%).

[0051] (4) Synthesis of Compound Z-2F

[0052] Under argon protection, compound 3 (0.654 mmol), 3-hexyl rhodanine (9.81 mmol) and 0.1 mL of piperidine were dissolved in dry chloroform (15 mL). The mixed solution was stirred at 60°C for 24 h, cooled to room temperature naturally, quenched with deionized water, extracted three times with chloroform (50 mL each time), and the solvent was removed by rotary evaporator. The crude product was purified by column chromatography on silica gel (eluent was petroleum ether and chloroform in a volume ratio of 1:1) to obtain a red solid compound Z-2F (yield of this step 65%), i.e., the desired organic small molecule donor material compound Z-2F containing two fluorine atoms. 1 H NMR spectrum is shown in Figure 4 .

[0053] Application of asymmetric donor materials with different fluorine contents in solar cells, organic light-emitting diodes and flexible displays.

[0054] Taking the application of the present invention in solar cells as an example, the specific implementation method is shown in Example 2.

[0055] Example 2: Preparation and characterization of organic solar cell devices

[0056] Preparation of organic photovoltaic devices: using the standard structure of ITO / anode interface layer / active layer / electron transport layer / top electrode.

[0057] (1) Substrate preparation: The finished ITO glass (indium tin oxide conductive glass) substrate was ultrasonically treated with detergent, deionized water, acetone and isopropyl alcohol, with each step cleaning for 11 minutes and dried with a nitrogen gas flow.

[0058] (2) Spin coating of anode interface layer: After ultrasonic cleaning of ITO glass (indium tin oxide conductive glass), oxygen-plasma treatment was used. PEDOT:PSS poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (ratio of 1:1, a mixed solution prepared at the time of purchase) was first spin coated on ITO at 5000 rpm. The annealing condition was 150°C for 15 min to obtain a surface film thickness of about 40 nm.

[0059] (3) Preparation of active layer: The small molecule compound Z-2F and the compound BTR-Cl prepared in Examples 1 and 2 were respectively used as donor materials and mixed with the acceptor L8-BO, and a mixed solvent of diiodomethane-chloroform (the volume ratio of diiodomethane to chloroform was 0.3 μL:100 μL) was added to prepare a blended solution (the total concentration of the donor and the acceptor was 20 mg / mL, and the mass ratio of the donor and the acceptor was 1.2:1). The blended solution was coated on the substrate in step (2) at a spin coating speed of 2000 rpm, and an active layer with a thickness of about 120 nm was coated on the surface of the substrate; the structural formula of the compound BTR-Cl is shown in Formula 2 below; the structural formula of the acceptor L8-BO is shown in Formula 3 below.

[0060]

[0061] (4) Spin coating of electron transport layer: The substrate obtained in step (3) was placed in a 60 nm culture dish, and then 60 μL of chlorobenzene was evenly applied on its surface, followed by solvent vapor annealing (85° C., 5 min). Next, an electron transport layer PNDIT-F3N thin film with a film thickness of 10-20 nm was coated on the above active layer at a spin coating speed of 3000 rpm; the structural formula of PNDIT-F3N is shown in Formula 4 below.

[0062]

[0063] (5) Evaporation of the top electrode: A 100 nm thick metal electrode (commonly used Ag, Al, etc.) is deposited on top of the electron transport layer by evaporation.

[0064] The specific organic solar cell efficiency is shown in Table 1 (the equipment used in the laboratory of the present invention is a solar simulator, which is calibrated with silicon solar cells, and all tests are measured under 1 simulated sunlight, 100 mW / cm2).

[0065] Table 1 Photoelectric conversion efficiency of all-small molecule photovoltaic devices

[0066] Active layer <![CDATA[V oc (V)]]> <![CDATA[J sc (mA / cm 2 )]]> FF(%) PCE(%) Compound Z-2F:L8-Bo 0.88 25.81 77.91 17.9 BTR-Cl:L8-Bo 0.86 24.52 76.31 16.1

[0067] From the data in Table 1, it can be seen that compared with the donor small molecule BTR-Cl containing a π-bridge, the PCE (energy conversion efficiency) of the asymmetric donor material Z-2F with different fluorine atom contents has been significantly improved, and the compound Z-2F has increased from 16.1% to 17.9% relative to the small molecule BTR-Cl. The filling factor (FF) has increased from 76.31% to 77.91%, and the current density (J sc ) from 24.52mA / cm 2 Increased to 25.81mA / cm 2 This type of donor material has a clear molecular structure in all-small molecule organic solar cells, and the differences between donor materials, acceptor materials and device batches are small, so it has unique advantages in commercialization. It is of great significance for us to build a high-efficiency organic solar cell system.

[0068] Figure 7 The normalized UV-visible absorption spectra of the compound Z-2F solution, Z-2F film and L8-BO film prepared in the present invention are shown in Figure 1. The results show that the compound Z-2F exhibits strong absorption in the range of 470 to 620 nm, which is complementary to the spectrum of L8-BO and is conducive to obtaining a higher short-circuit current (J sc ). The strongest absorption peak from the solution state to the film state has a red shift of about 50nm, which indicates that stronger π-π stacking is generated during the film formation process. In the film, Z-2F has a stronger shoulder peak, indicating that the molecules in the pure film state are well stacked and have strong interactions between molecules, which is conducive to the formation of a good morphology of the blended film.

[0069] Figure 8The cyclic voltammetry curves of the compounds Z-2F and L8-BO prepared by the present invention (scanning speed: 0.05V per second) show that the HOMO energy level of the compound Z-2F is -11.35eV, and its LUMO energy level is -2.85eV, which matches well with the energy level of L8-BO, which is conducive to exciton dissociation, and is expected to generate a higher open circuit voltage and improve the photoelectric conversion efficiency of photovoltaic devices.

[0070] The solar cell comprises a water-surface floating organic solar cell; the water-surface floating organic solar cell comprises a solar panel manufactured using Z-2F and a water-surface floating structure, wherein the water-surface floating structure enables the solar panel to float on the water surface.

[0071] Example 3: Floating Application of Organic Solar Cells

[0072] In Example 2, solar cells with conventional structures such as ITO / PEDOT:PSS / active layer / PNDIT-F3N / Ag were prepared, and their photovoltaic performance was tested. A water surface floating system was added to the bottom of the solar panel to increase the application of water surface photovoltaics. The water surface floating system can be composed of a floating structure 1, a PV panel 2, a fixed bracket 3 and a hinge structure 4, which can make the solar panel float on the water surface and adjust the inclination angle of the solar panel. The floating structure 1 can select a common floating structure such as a buoy; when the solar cells are placed on the water surface at two inclination angles of 0° and 30°, they can act as a thermal barrier to block sunlight and heat flux, significantly reduce the surface temperature of the water, and slow down the evaporation of water; compared with ground-mounted photovoltaic modules, the operating temperature is reduced, which increases the life of the solar photovoltaic modules. The structural form of the water surface floating system is as follows Fig. 9 Shown: The figure shows a 30° inclination angle.

[0073] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. An asymmetric donor material with different fluorine contents, characterized in that: Specifically, it is an organic small molecule donor material with different asymmetric two-dimensional side chains containing fluorine atoms, and its structural formula is shown in Formula 1:

2. The method for preparing asymmetric donor materials with different fluorine contents according to claim 1, characterized in that: The specific steps include: S1: Using tetrahydrofuran as solvent and iodine as initiator, magnesium powder and 4-bromo-1,2-difluorobenzene are added, and the mixture is refluxed at 70°C for 4h to perform reflux reaction until magnesium is completely consumed, and then naturally cooled to room temperature to obtain Grignard reagent 1. Grignard reagent 1 is added dropwise to a toluene solution of benzo[1,2-b:4,5-b']dithiophene-4,8-dione, and stirred at room temperature. At the same time, using tetrahydrofuran as solvent and iodine as initiator, magnesium powder, 5-bromo-3-chloro-2-(2-hexyldiethyl)thiocin, and The mixture was refluxed at 70°C for 2h until magnesium was completely consumed, and naturally cooled to room temperature to obtain Grignard reagent 2, and then the newly prepared Grignard reagent 2 was transferred to a dropping funnel and slowly dripped into the mixed solution to which Grignard reagent 1 was added. Subsequently, the mixture was stirred at room temperature overnight, and then dihydrate tin (II) chloride dissolved in 10% HCl was added at room temperature, and then the resulting solution was stirred at 50°C for 3 hours; after completion, the reaction was naturally cooled to room temperature and poured into water to obtain compound 1; S2: under the protection of argon, n-butyl lithium solution was added dropwise to the tetrahydrofuran solution containing compound 1 at -78°C. After the addition, the mixture was stirred at -78°C for 1 hour, and then compound 1 was added. The mixture was continuously stirred at -78°C for 1 hour, and the temperature was naturally raised to room temperature for reaction for 12 hours. Subsequently, the mixture was cooled to room temperature, and a tin reagent solution was added; then the mixture was stirred at 50°C for another 3 hours to generate compound 2; the tin reagent solution was prepared by dissolving tin (II) chloride dihydrate in 10% HCl; S3: Under argon protection, using tetrakis(triphenylphosphine)palladium as a catalyst and toluene as a solvent, compound 2 and 5"-bromo-3',3"-dihexyl-[2,2':5',2"-terthiophene]-5-carbaldehyde were refluxed at 110°C for 8 to 10 hours to produce a Stille coupling reaction to obtain compound 3; S4: Under argon protection, compound 3, 3-hexylrhodanine and a base were added to the solvent chloroform, and a Knoevenagel condensation reaction was carried out at 60°C to connect the rhodanine end groups to obtain an organic small molecule donor material containing an asymmetric two-dimensional side chain, referred to as compound Z-2F.

3. The method for preparing asymmetric donor materials with different fluorine contents according to claim 2, characterized in that: The molar ratio of the three substances of 5-bromo-3-chloro-2-(2-hexyldiethyl) thiocine, 4-bromo-1,2-difluorobenzene and benzo[1,2-b:4,5-b']dithiophene-4,8-dione in S1 is 1:2:2.3, and the molar ratio of the benzo[1,2-b:4,5-b']dithiophene-4,8-dione to the tin reagent is 1:

5.

4. The method for preparing asymmetric donor materials with different fluorine contents according to claim 2, characterized in that: The molar ratio of compound 1 to the tin reagent in S2 is 1:2.5; the molar ratio of n-butyl lithium to compound 1 is 1:3.

5.

5. The method for preparing asymmetric donor materials with different fluorine contents according to claim 2, characterized in that: The optimal conditions for the reflux reaction in S3 are reflux reaction at 110° C. for 9 hours; the molar ratio of compound 2 to 5”-bromo-3',3”-dihexyl-[2,2':5',2”-terthiophene]-5-carbaldehyde in S3 is 1:15, and the molar ratio of the catalyst to compound 3 is 20 mg:10.31 mmol.

6. The method for preparing asymmetric donor materials with different fluorine contents according to claim 2, characterized in that: The reaction time of the condensation reaction in S4 is 24 h; the molar ratio of 3-hexylrhodanine to compound 3 in S4 is 15:1; and the molar ratio of the base to compound 3 is 1.5 mL:0.654 mmol.

7. Use of the asymmetric donor materials with different fluorine contents according to claims 1-6 in the preparation of the following functional energy devices: solar cells, organic light emitting diodes and flexible displays.

8. The use of asymmetric donor materials with different fluorine contents according to claim 7, characterized in that: The solar cell comprises a water-surface floating organic solar cell; the water-surface floating organic solar cell comprises a solar panel made of Z-2F material and a water-surface floating structure.

Images