A small molecule electron donor material, its preparation method, and its application

Abstract

This invention belongs to the field of functional materials, specifically relating to a small molecule electron donor material, its preparation method, and its applications. The small molecule electron donor provided by this invention has a relatively simple preparation method with strong operability, suitable for large-scale preparation. Furthermore, this small molecule electron donor exhibits good solubility, stability, photoelectric properties, and solution processability, and can be used as an electron donor material for polymer organic solar cells, significantly improving the flexibility of polymer solar cells.

Description

Technical Field

[0001] This invention belongs to the field of functional materials, specifically relating to a small molecule electron donor material, its preparation method, and its application. Background Technology

[0002] Organic solar cells, with their advantages of being lightweight, flexible, and solution-processable, have become a hot research topic in the industry in recent years. All-small molecule solar cells, due to their well-defined material structures and lack of batch-to-batch variation, possess significant industrialization potential. In the past two years, organic solar cells have developed rapidly; the photoelectric conversion efficiency of all-small molecule organic photovoltaic devices using non-fullerene as acceptor materials has exceeded 17%. However, the small molecular weight of these materials leads to easily altered microstructures in flexible devices, reducing their stability and hindering the marketization of organic photovoltaics.

[0003] Polymeric small-molecule electron donors possess high molecular weights and flexible alkyl chains within the molecule, which enhances the material's stretchability. These donors not only offer numerous modification sites for renewing the material structure but also maintain a favorable morphology of the active layer, improving the photovoltaic stability of the device. However, the variety of current polymeric small-molecule electron donor materials is limited, and their photovoltaic performance is generally low. Therefore, developing polymeric small-molecule electron donor materials can further improve the stretchability of materials, thereby enhancing the stability of flexible photovoltaic devices and facilitating the commercial application of organic photovoltaic materials. Summary of the Invention

[0004] In view of the problems of poor stretchability of small molecule donors and poor stability of flexible all-small molecule organic solar cells in the existing technology, the purpose of this invention is to provide a poly-small molecule electron donor material.

[0005] The present invention also provides a method for preparing the above-mentioned small molecule electron donor material.

[0006] Another object of the present invention is to provide the application of the above-mentioned small molecule electron donor material as an active layer material in photovoltaic devices.

[0007] To achieve the above and other related objectives, the first aspect of the present invention provides a small molecule electron donor material: the molecular structure of the small molecule electron donor material is as follows: .

[0008] The present invention also provides a method for preparing the above-mentioned small molecule electron donor material, comprising the following steps: reacting a dibromo group compound and bis(trimethyltin)thiophene under the action of a catalyst to obtain a small molecule electron donor.

[0009] Preferably, the molar ratio of the dibromo-based compound to the bis(trimethyltin)thiophene is 1:1; the catalyst is tetra(triphenylphosphine)palladium; and the ratio of the dibromo-based compound to the catalyst is 0.05 mmol: 10 mg.

[0010] Preferably, the reaction is carried out at a temperature of 100-110°C for 24 hours.

[0011] In the synthesis of small molecule electron donor materials, the dibromo compounds used in this invention are prepared by the following method: (1) (4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophen-2,6-diyl)bis(trimethylstanane) and 5''-bromo-3',3''-dihexyl-[2,2':5',2''-trithiophene]-5-carboxaldehyde react to give 5'',5'''''-bis(4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophen-2,6-diyl)bis(3',3''-dihexyl-[2''',2'''':5'''',2'''''-trithiophene]-5-carboxaldehyde); (2) 2-Thiothiazolidin-4-one and 6-bromohexyl5-bromothiophen-2-carboxylate react with sodium hydroxide to give 6-(4-oxo-2-thiothiazolidin-3-yl)hexyl5-bromothiophen-2-carboxylate; (3) 5'',5''''-bis(4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophen-2,6-diyl)bis(3',3''-dihexyl-[2''',2'''':5'''',2''''-terthiophene]-5-carboxaldehyde) and 6-(4-oxo-2-thiothiazolidin-3-yl)hexyl5-bromothiophene-2-carboxylate under piperidine catalysis Under the action of , ((5E,5'E)-(((4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophen-2,6-diyl)bis(3',3''-dihexyl-[2,2':5',2''-trithiophene]-5'',5-diyl))bis(methylene))bis(4-oxo-2-thiothiazolidin-3-yl-5-ylidene))bis(hexane-6,1-diyl)bis(5-bromothiophene-2-carboxylate) (a dibromo compound).

[0012] The present invention also provides the application of the above-mentioned small molecule electron donor materials as active layer materials in photovoltaic devices.

[0013] Preferably, the active layer material further includes an electron acceptor material.

[0014] Preferably, the electron acceptor material is selected from PC. 71 At least one of BM, ITIC, Y6, L8-BO and PYIT.

[0015] The specific reactive molecular formula of the small molecule electron donor material provided by this invention is as follows:

[0016] The present invention has the following beneficial effects: (1) The small molecule electron donors provided by the present invention have a relatively simple preparation method and the method is highly operable and suitable for large-scale preparation; (2) The small molecule electron donor of the present invention has good solubility, stability, photoelectric properties and solution processability, and can be used as an electron donor material for polymer organic solar cells; (3) The small molecular electron donor PSM1 of the present invention has a high molecular weight, good stretchability, and good stability of flexible devices. (4) The small molecule electron donor of the present invention significantly improves the device stability of flexible polymer solar cells. Attached Figure Description

[0017] Some specific embodiments of the invention are described in detail with reference to the accompanying drawings, by way of example and not limitation. The same reference numerals in the drawings designate the same or similar parts or portions. Those skilled in the art will understand that these drawings are not necessarily drawn to scale. The objectives and features of the invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which: Figure 1 It is the (5'',5'''''-bis(4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophen-2,6-diyl)bis(3',3''-dihexyl-[2''',2'''':5'''',2''''-terthiophene]-5-carboxaldehyde) prepared in Example 1. 1 H NMR spectrum; Figure 2 The 6-(4-oxo-2-thiothiazolidin-3-yl)hexyl5-bromothiophene-2-carboxylate ester prepared in Example 1 1 H NMR spectrum; Figure 3 The dibromo compound prepared in Example 1 1 H NMR spectrum; Figure 4 This is the ultraviolet-visible absorption spectrum of the small molecule electron donor of the present invention; Figure 5 The present invention relates to a photovoltaic device made of small molecule electron donors and Y6. JV Line graph; Figure 6 This is a schematic diagram of the structure of a flexible polymer organic solar cell device prepared by the small molecule electron donor of the present invention; Figure 7 The bending force test of the flexible polymer solar cell device prepared by the small molecule electron donor of the present invention is shown. Figure 8 This is a test graph showing the photovoltaic efficiency and tensile stability of a flexible polymer organic solar cell device prepared using the small molecule electron donor of the present invention. Detailed Implementation

[0018] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but these are not intended to limit the scope of protection of the present invention.

[0019] Example 1 ① Preparation of (5'',5'''''-bis(4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophen-2,6-diyl)bis(3',3''-dihexyl-[2''',2'''':5'''',2''''-terthiophene]-5-carboxaldehyde) (compound 3): 0.5 mmol of (4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl)bis(trimethylstanane) (compound 1) and 1.5 mmol of 5''-bromo-3',3''-dihexyl-[2,2':5',2''-tristhiophene]-5-carboxaldehyde (compound 2) were dissolved in 20 mL of toluene. 100 mg of tetrakis(triphenylphosphine)palladium was added, and the mixture was refluxed at 110 °C for 24 hours. After the reaction was complete, the solvent was evaporated to dryness, and the mixture was extracted three times with dichloromethane and dried over anhydrous magnesium sulfate. The solvent was then evaporated to dryness, and the crude product was purified by silica gel column chromatography using dichloromethane as the eluent to give a red solid (0.15 g, 70% yield). 1 H NMR spectrum as shown Figure 1 As shown.

[0020] The proton NMR spectrum of product compound 3: 1H NMR (400MHz, CDCl3) δ9.86 (s, 2H), 7.72 (s, 2H), 7.68 (s, 2H), 7.23 (s, 4H), 7.12 (s, 2H), 7.02 (s, 2H), 2.83 (m, 4H), 2.66 (m, 8H), 1.71 (m,2H), 1.61–1.25 (m, 48H), 1.00-0.83 (m, 24H). ② Preparation of 6-(4-oxo-2-thiothiazolidin-3-yl)hexyl5-bromothiophene-2-carboxylate (compound 6): 2-Thiothiazolidin-4-one (compound 4) (3 g, 22.56 mmol), 6-bromohexyl5-bromothiophene-2-carboxylate (compound 5) (9.18 g, 24.81 mmol), and sodium hydroxide (1.8 g, 45.12 mmol) were dissolved in 50 mL of DMF and refluxed at 90 °C for 10 hours. After the reaction, the mixture was washed with brine, extracted three times with dichloromethane, and dried over anhydrous magnesium sulfate. The solvent was then evaporated to dryness, and the crude product was purified by silica gel column chromatography using dichloromethane as the eluent to give a pale yellow oily liquid (6.65 g, 70% yield). The proton NMR spectrum of product compound 6 is shown below. Figure 2 As shown.

[0021] The proton NMR spectrum of product compound 6: 1 H NMR (400MHz, CDCl3) δ7.54(s,1H), 7.07(s,1H), 4.28(s,2H), 3.99(s,2H), 1.75(s,2H), 1.68(t,2H), 1.47(t,4H), 1.25(t,2H).

[0022] ③ Preparation of the dibromo group compound (compound 7): (5'',5'''''-bis(4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophen-2,6-diyl)bis(3',3''-dihexyl-[2''',2'''':5'''',2''''-trithiophene]-5-carboxaldehyde) (compound 1, 0.15 g, 0.098 mmol) and 6-(4-oxo-2-thiothiazolidin-3-yl)hexyl 5-bromothiophene-2-carboxylate (compound 6, 0.41 g, 0.98 mmol) were dissolved in 20 mL of chloroform, 1 mL of piperidine was added at room temperature, and the reaction was carried out at 60 °C for 24 hours. The reaction result was... After washing with brine, the mixture was extracted three times with dichloromethane and dried over anhydrous magnesium sulfate. The solvent was then evaporated to dryness, and the crude product was purified by silica gel column chromatography using dichloromethane as the eluent to give a purple-red solid, which is the dibromo compound, ((5E,5'E)-(((4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophen-2,6-diyl)bis(3',3''-dihexyl-[2,2':5',2''-terthiophene]-5'',5-diyl))bis(methylene))bis(4-oxo-2-thiothiazolidin-3-yl-5-ylidene))bis(hexane-6,1-diyl)bis(5-bromothiophene-2-carboxylate (0.18 g, yield 80%).

[0023] The proton NMR spectrum of product compound 7: 1 H NMR (400MHz, CDCl3) δ7.76(s,2H), 7.54(s,2H), 7.46(s,4H), 7.29(s,2H), 7.24(s,2H), 7.14(s,2H), 7.01 (s,4H), 7.96(s,2H), 4.28(s,4H), 3.99(s,4H), 2.83 (m, 8H), 2.66 (m, 12H), 1.71 (m, 10H), 1.61–1.25 (m, 52H), 1.00-0.83 (m, 24H).

[0024] The proton NMR spectrum of the dibromo group compound is as follows: Figure 3 As shown.

[0025] ④ Polymeric small molecule electron donor materials 0.05 mmol of a dibromo group compound and 0.05 mmol of bis(trimethyltin)thiophene were dissolved in 6 mL of toluene, and 10 mg of tetra(triphenylphosphine)palladium was added. The reaction was carried out at 110 °C for 24 hours. After the reaction was completed, the product was precipitated in methanol, and the solid was extracted in a Soxhlet extractor with methanol, n-hexane, and chloroform in sequence. Finally, the solution was collected and evaporated to dryness to obtain a purple-black solid, which was the polysmall molecule electron donor (PSM1).

[0026] The molecular weight of the small molecule electron donor material prepared in Example 1 was found to be 15.3 kDa.

[0027] The prepared small molecule electron donor PSM1 was subjected to UV-Vis absorption testing, such as... Figure 4 As shown. From Figure 4 As can be seen, the main absorption peak of the small molecule electron donor (PSM1) is at 657 nm.

[0028] Example 2 (1) Fabrication and characterization of flexible organic photovoltaic devices The device structure is ITO-polyethylene naphthalate / PEDOT:PSS / PSM1:Y6 / PFN-Br / Ag. The ITO glass substrate was ultrasonically cleaned sequentially with soapy water, deionized water, acetone, and isopropanol, then vacuum-dried overnight at 110°C and treated with ozone for 20 minutes. PEDOT:PSS was then spin-coated onto the cleaned ITO glass substrate at 4000 rpm for 20 seconds and annealed at 200°C for 30 minutes. A mixture of chloronaphthalene additive, poly(small molecule) electron donors PSM1 and Y6 (PSM1 and Y6 mass ratio 1:1) was dissolved in chloroform (CF), with a chloronaphthalene concentration of 18 mg / mL. The active layer was then spin-coated at 3000 rpm for 30 seconds. A PFN-Br electron transport layer (concentration 0.5 mg / mL) was then spin-coated at 3000 rpm, and after drying, an Ag electrode layer was vacuum-deposited.

[0029] The fabricated solar cell device, measured by a Keithley 2400 under simulated AM1.5G light, showed a photoelectric conversion efficiency of 12.56% and an open-circuit voltage of [missing value]. V OC The short-circuit current density is 0.915 eV. J SC =21.39 mA cm -2 The fill factor FF = 0.642.

[0030] (2) Stability testing of flexible organic photovoltaic devices The fabricated flexible organic solar cell device was bent for 10 minutes, and its photovoltaic performance was measured under AM1.5G simulated light. The measured photoelectric conversion efficiency was 10.86%, and the open-circuit voltage was [not specified]. V OC The short-circuit current density is 0.901 eV. J SC =20.21 mA cm -2The fill factor FF = 0.596. The flexible device, after bending, still maintains 85% of the initial device efficiency, demonstrating excellent device stability.

[0031] Figure 5 The flexible photovoltaic device made of the small molecule electron donor PSM1 and Y6 of this invention. JV A line graph. (From...) Figure 5 As shown, the flexible photovoltaic device prepared by this invention has excellent photovoltaic performance and high photoelectric conversion efficiency, indicating that the PSM1 prepared by this invention is a novel donor material with excellent performance.

[0032] Figure 6 This is a schematic diagram of the structure of a flexible polymer solar cell device fabricated using the small molecule electron donor (PSM1) of the present invention.

[0033] Figure 7 This is a bending force test (three times) of a flexible polymer solar cell device fabricated using the small molecule electron donor (PSM1) of this invention. Figure 7 It can be seen that during the three bending force tests, the film experienced no drastic changes in stress throughout the process, indicating that the small molecule electron donor (PSM1) active layer prepared in this invention is stably bonded to the flexible substrate, and the mechanical integrity of the film is well maintained, making it suitable for flexible and repeatedly bendable photovoltaic device applications.

[0034] Figure 8 This is a photovoltaic efficiency stability test chart of a flexible polymer solar cell device prepared using the small molecule electron donor PSM1 of this invention. Figure 8 As shown, after a bending test of about 10 minutes, the photovoltaic efficiency of the device still remained at 85% of the initial efficiency, indicating that the flexible device based on the small molecule electron donor PSM1 has excellent mechanical tensile stability.

[0035] The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, those skilled in the art will know that there will be changes in the specific implementation methods and application scope according to the embodiments of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A polyoligomeric electron donor material, characterized in that The molecular structure of the small molecule electron donor material is as follows: 。 2. A method for preparing the poly(small molecule) electron donor material as described in claim 1, characterized in that, The process includes the following steps: reacting a dibromo-based compound and bis(trimethyltin)thiophene under the action of a catalyst to obtain a small molecule electron donor.

3. The preparation method according to claim 2, characterized in that, The molar ratio of the dibromo-based compound to bis(trimethyltin)thiophene is 1:1; the catalyst is tetra(triphenylphosphine)palladium; and the ratio of the dibromo-based compound to the catalyst is 0.05 mmol: 10 mg.

4. The preparation method according to claim 2 or 3, characterized in that, The reaction was carried out at a temperature of 100-110℃ for 24 hours.

5. The preparation method according to claim 2, characterized in that, The dibromo group compound was prepared by the following method: (1) (4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophen-2,6-diyl)bis(trimethylstanane) and 5''-bromo-3',3''-dihexyl-[2,2':5',2''-trithiophene]-5-carboxaldehyde react to give 5'',5'''''-bis(4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophen-2,6-diyl)bis(3',3''-dihexyl-[2''',2'''':5'''',2'''''-trithiophene]-5-carboxaldehyde); (2) 2-Thiothiazolidin-4-one and 6-bromohexyl5-bromothiophen-2-carboxylate react with sodium hydroxide to give 6-(4-oxo-2-thiothiazolidin-3-yl)hexyl5-bromothiophen-2-carboxylate; (3) 5'',5''''-bis(4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophen-2,6-diyl)bis(3',3''-dihexyl-[2''',2'''':5'''',2''''-terthiophene]-5-carboxaldehyde) and 6-(4-oxo-2-thiothiazolidin-3-yl)hexyl 5-bromothiophene-2-carboxylate under piperidine catalysis The dibromoyl compound, ((5E,5'E)-(((4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophen-2,6-diyl)bis(3',3''-dihexyl-[2,2':5',2''-trithiophene]-5'',5-diyl))bis(methimyl))bis(4-oxo-2-thiothiazolidin-3-yl-5-ylidene))bis(hexane-6,1-diyl)bis(5-bromothiophene-2-carboxylate).

6. The application of the small molecule electron donor material as described in claim 1 in the active layer material of a photovoltaic device.

7. The application according to claim 6, characterized in that, The active layer material also includes an electron acceptor material.

8. The application according to claim 7, characterized in that, The electron acceptor material is selected from PC 71 at least one of BM, ITIC, Y6, L8-BO, and PYIT.

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