An organic hole transporting material, its preparation method and application

Abstract

The present invention relates to the field of organic battery materials, and specifically discloses an organic hole transport material, a preparation method thereof and an application. The organic hole transport material uses 1,2,4,5-tetrafluorobenzene as the central unit and spirofluorene oxanthrene as the two-side structure, and is synthesized through a coupling reaction. The organic hole transport material has good solubility, high quantum efficiency and hole mobility. When applied as a hole transport layer in perovskite solar cells, it can effectively improve the photoelectric conversion efficiency and stability of the solar cells, and provides good reference significance for the research of high-performance hole transport materials.

Description

Technical Field

[0001] The present invention relates to the field of organic battery materials, and specifically discloses an organic hole transport material, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, organic-inorganic hybrid perovskite solar cells (PSCs) have become a research hotspot of a new generation of solar cells due to advantages such as wide material sources, simple preparation processes, and high efficiency. Among them, the hole transport material in perovskite solar cells has functions such as extracting and transporting holes, suppressing charge recombination, and preventing the perovskite light-harvesting layer from being eroded by moisture, and is an indispensable part of perovskite solar cells, and has already become a research hotspot.

[0003] Spirofluoreneoxanthene (SFX) is a classic spiro compound composed of a fluorene ring and an oxanthene ring, and a spiro atom is formed at the bridging atom of the fluorene ring. SFX has the following basic characteristics: a cross-shaped geometric configuration, a steric hindrance effect, and a conjugation interruption of the spiro atom. This unique collective configuration and the inherent steric hindrance are beneficial to suppressing the stacking of molecules. The spiroconjugation effect caused by the conjugation interruption can reduce the overall conjugation degree of the molecule, is suitable for designing wide-bandgap molecules, and the spiro ring structure itself can improve the rigidity of the molecule and increase the thermal stability of the molecule, thereby extending the service life of perovskite solar cells.

[0004] In the prior art, the hole transport materials used in perovskite solar cells are complex to synthesize, difficult to purify, have poor solubility, and unstable performance, and do not have a high hole mobility. While high-hole-transport-rate materials such as Spiro-OMeTAD materials have problems such as high synthesis difficulty, many synthesis steps, high purification difficulty, and low yield. Therefore, it is of great significance to develop a hole transport material with simple synthesis, high hole mobility, and a suitable energy level structure for the development of perovskite solar cells. Summary of the Invention

[0005] Aiming at the technical problems in the prior art that the hole transport materials used in perovskite solar cells are complex to synthesize, difficult to purify, have poor solubility, unstable performance, and do not have a high hole mobility, which affect the use effect of battery devices, the present invention provides an organic hole transport material, a preparation method thereof, and an application thereof. The organic hole transport material uses 1,2,4,5-tetrafluorobenzene as the central unit and spirofluoreneoxanthene as the two-side structure. The organic hole transport material has good solubility, high quantum efficiency, and high hole mobility. When applied as a hole transport layer in perovskite solar cells, it can effectively improve the photoelectric conversion efficiency and stability of solar cells, and provides good reference significance for the research of high-performance hole transport materials.

[0006] To solve the above technical problems, the technical solution provided by the present invention is as follows:

[0007] In the first aspect of the present invention, an organic hole transporting material is provided, which at least includes the following steps: The structure of the organic hole transporting material is shown in Formula 1:

[0008]

[0009] R1, R2, and R3 are selected from H or F, wherein at least two of R1, R2, and R3 are hydrogen atoms.

[0010] Compared with the prior art, the present invention provides a novel organic hole transporting material. The organic hole transporting material uses 1,2,4,5-tetrafluorobenzene and spirofluorene oxadiazole derivatives as the main raw materials. Based on the spirofluorene oxadiazole skeleton with high steric hindrance and high hole mobility, through a coupling reaction, 1,2,4,5-tetrafluorobenzene is introduced as an intermediate bridging unit. The fluorene end or oxadiazole end of spirofluorene oxadiazole is coupled with 1,2,4,5-tetrafluorobenzene to form a donor-acceptor-donor (D-A-D) type conjugate system. The introduction of fluorine atoms can regulate the energy level and band gap of the material, making the compound have a deeper HOMO energy level, thereby improving the device efficiency. In addition, using this organic hole transporting material in perovskite solar cell devices can achieve a higher hole mobility, external quantum efficiency, and excellent device stability, and the synthesis is simple, and the product has good solubility, providing more ideas for the preparation of perovskite solar cells.

[0011] Preferably, the structure of the organic hole transporting material is

[0012] any one of

[0013] In the second aspect of the present invention, a preparation method of the organic hole transporting material is provided, which at least includes the following steps: Under an inert atmosphere, 1,2,4,5-tetrafluorobenzene, the spirofluorene oxadiazole derivative shown in Formula 2, an acid-binding agent, a palladium catalyst, and a phosphorus-containing ligand are subjected to a Suzuki coupling reaction in an organic solvent to obtain the organic hole transporting material;

[0014] Among them, the structure of Formula 2 is as follows:

[0015]

[0016] R1 and R2 are selected from H or F, wherein at least one of R1 and R2 is a hydrogen atom.

[0017] Preferably, the spirofluorene oxadiazole derivative is

[0018] any one of

[0019] Preferably, the phosphorus-containing ligand is any one of di-tert-butylmethylphosphonium tetrafluoroborate, 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl, tri-tert-butylphosphine, 1,1'-binaphthalene-2,2'-bis(diphenylphosphine), tris(o-tolyl)phosphine, or 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene.

[0020] Preferably, the acid-binding agent is any one of calcium carbonate, cesium carbonate, sodium carbonate, potassium phosphate, potassium tert-butoxide, or sodium tert-butoxide.

[0021] Preferably, the palladium catalyst is any one of tetrakis(triphenylphosphine)palladium, [1,1-bis(diphenylphosphino)ferrocene]dichloropalladium, or palladium acetate.

[0022] Preferably, the molar ratio of the spirofluoreneoxanthrene derivative to 1,2,4,5-tetrafluorobenzene is 1:1 - 1.2.

[0023] Preferably, the molar ratio of the spirofluoreneoxanthrene derivative to the palladium catalyst is 5 - 50:1.

[0024] Preferably, the molar ratio of the spirofluoreneoxanthrene derivative to the acid-binding agent is 1:2 - 1.

[0025] Preferably, the molar ratio of the spirofluoreneoxanthrene derivative to the phosphorus-containing ligand is 1:5 - 10.

[0026] Preferably, the temperature of the Suzuki coupling reaction is 80°C - 120°C, and the reaction time is 12 h - 48 h.

[0027] Preferably, after the Suzuki coupling reaction is completed, the system needs to be quenched, extracted, dried, and separated by column chromatography to obtain the organic hole transporting material.

[0028] Preferably, the quenching agent is a saturated disodium ethylenediaminetetraacetate solution with a pH of 7.5 - 8.

[0029] Preferably, the extraction solvent for extraction is dichloromethane.

[0030] Preferably, the drying is carried out using anhydrous sodium sulfate for drying.

[0031] Preferably, the eluent for column chromatography separation is petroleum ether and ethyl acetate with a volume ratio of 18 - 22:1.

[0032] Preferably, the preparation method of the spirofluoreneoxanthrene derivative comprises the following steps:

[0033] Under an inert atmosphere, 2-bromofluorene-9-one, methanesulfonic acid, and a phenolic ligand are mixed evenly and then subjected to a dehydration condensation reaction in an organic solvent to obtain the spirofluoreneoxanthrene derivative.

[0034] Preferably, the phenolic ligand is any one of phenol, 4-fluorophenol, or 3-fluorophenol.

[0035] Preferably, the molar ratio of the 2-bromofluorene-9-one, methanesulfonic acid, and phenolic ligand is 1 - 1.1:4 - 5:10 - 12.

[0036] Preferably, the temperature of the dehydration condensation reaction is 145°C - 155°C, and the reaction time is 45 h - 50 h.

[0037] Preferably, after the dehydration condensation reaction is completed, the reaction system needs to be poured into anhydrous methanol, filtered, and washed to obtain the spirofluoreneoxazine derivative.

[0038] Preferably, the mass ratio of the anhydrous methanol to the total mass of the mixture of 2-bromofluorene-9-one, methanesulfonic acid, and phenolic ligand is 10 - 15:1.

[0039] The third aspect of the present invention provides a hole transport layer comprising the organic hole transport material.

[0040] The fourth aspect of the present invention provides a perovskite solar cell comprising the hole transport layer.

[0041] Preferably, the perovskite solar cell sequentially comprises a conductive glass substrate layer, a titanium dioxide layer, a perovskite layer, a hole transport layer, and a metal electrode.

[0042] Preferably, the method for preparing the hole transport layer comprises the following steps: Dissolve the organic hole transport material in chlorobenzene to obtain an organic hole transport material solution, add 4-tert-butylpyridine and lithium bis(trifluoromethanesulfonyl)imide to the organic hole transport material solution, mix evenly, and then spin-coat it onto the perovskite layer to obtain the hole transport layer.

[0043] Preferably, the mass ratio of the organic hole transport material, 4-tert-butylpyridine, and lithium bis(trifluoromethanesulfonyl)imide is 1 - 2:1.5 - 3.5:1.2 - 3.

[0044] Preferably, the concentration of the organic hole transport material solution is 30 mg / mL - 60 mg / mL.

[0045] Preferably, the spin-coating speed is 4000 rpm - 4100 rpm, and the spin-coating time is 22 s - 27 s.

[0046] Preferably, the method for preparing the conductive glass substrate layer comprises the following steps: After drying the clean conductive glass, immerse it successively in ultrapure water, acetone, and isopropyl alcohol, perform ultrasonic cleaning, and after drying, perform ultraviolet-ozone treatment to obtain the conductive glass substrate layer.

[0047] Preferably, the time for ultrasonic cleaning is 25 min - 35 min.

[0048] Preferably, nitrogen is used for drying, and the gas flow rate is 0.03 L / min - 0.05 L / min.

[0049] Preferably, the time for ultraviolet-ozone treatment is 20 min - 35 min.

[0050] Preferably, the method for preparing the titanium dioxide layer comprises the following steps: placing a titanium tetrachloride solution on the conductive glass substrate layer, drying, rinsing, drying, and annealing to obtain the titanium dioxide layer.

[0051] Preferably, the drying temperature is 70°C - 75°C, and the drying time is 1 h - 2 h.

[0052] Preferably, nitrogen is used for drying, and the gas flow rate is 0.03 L / min - 0.05 L / min.

[0053] Preferably, the annealing temperature is 170°C - 190°C, and the annealing time is 25 min - 35 min.

[0054] Preferably, the thickness of the titanium dioxide layer is 35 nm - 45 nm.

[0055] Preferably, the method for preparing the perovskite layer comprises the following steps: subjecting the conductive glass substrate deposited with the titanium dioxide layer to ultraviolet-ozone treatment, then coating the precursor solution on the titanium dioxide layer by spin coating, and after spin coating, performing annealing treatment to obtain the perovskite layer.

[0056] Preferably, the method for preparing the precursor solution comprises the following steps: mixing lead iodide, 1H-imidazol-1-yl(2-methyl-3-furyl)methanone, and methylammonium iodide uniformly, and then dissolving them in a mixed solution of anhydrous N,N-dimethylformamide and anhydrous dimethyl sulfoxide with a volume ratio of 3.8 - 4:1.

[0057] Preferably, the dosage of lead iodide is 1 g - 5 g

[0058] Preferably, the mass ratio of lead iodide, 1H-imidazol-1-yl(2-methyl-3-furyl)methanone, and methylammonium iodide is 20 - 25:15 - 17:3 - 4.

[0059] Preferably, the mass concentration of the precursor solution is 0.05 g / mL - 1 mg / mL.

[0060] Preferably, the spin-coating operation is to spin-coat the precursor at a speed of 1000 rpm - 1100 rpm for 3 s - 6 s, then adjust the spin-coating speed to 3800 rpm - 4200 rpm and spin-coat for 8 s - 12 s, and then drop 130 mL - 170 mL of chlorobenzene and spin-coat for 30 s to obtain a spin-coated perovskite layer.

[0061] Preferably, the temperature of the annealing treatment is 140°C - 160°C, and the treatment time is 25 min - 35 min.

[0062] Preferably, the preparation method of the metal electrode includes the following steps: depositing gold on the surface of the hole transport layer by thermal evaporation deposition, with a thickness of 90 nm - 110 nm.

[0063] The present invention provides an organic hole transport material, which is applied to perovskite solar cells. The organic hole transport material is simple to synthesize, has good solubility, stable performance, high quantum efficiency and hole mobility, can effectively improve the photoelectric conversion efficiency and stability of perovskite solar cells, and provides a good reference for the research of high-performance hole transport materials. Description of the Drawings

[0064] Figure 1 1H NMR spectrum (500 MHz, CDCl3, ppm) of the product of Example 1; 1 1H NMR spectrum (500 MHz, CDCl3, ppm) of the product of Example 1;

[0065] Figure 2 13C NMR spectrum (400 MHz, CDCl3, ppm) of the product of Example 1; 13 13C NMR spectrum (400 MHz, CDCl3, ppm) of the product of Example 1;

[0066] Figure 3 1H NMR spectrum (500 MHz, CDCl3, ppm) of the product of Example 2; 1 1H NMR spectrum (500 MHz, CDCl3, ppm) of the product of Example 2;

[0067] Figure 4 13C NMR spectrum (400 MHz, CDCl3, ppm) of the product of Example 2; 13 13C NMR spectrum (400 MHz, CDCl3, ppm) of the product of Example 2;

[0068] Figure 5 Thermogravimetric analysis diagram and DSC test diagram of the product of Example 2;

[0069] Figure 6 Hole transport performance test diagram of the product of Example 2;

[0070] Figure 7 Cyclic voltammetry curve diagram of the product of Example 2;

[0071] Figure 8J-V characteristic curve of the perovskite solar cell prepared in Test Example 4; Detailed implementation mode

[0072] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0073] Example 1

[0074] This example provides an organic hole transporting material, and the specific preparation process is as follows:

[0075] Step 1: Under an inert atmosphere, 1 g (3.86 mmol) of dry 2-bromofluorene-9-one, 1 ml (15.44 mmol) of methanesulfonic acid, and 3.6 g (38.6 mmol) of phenol are mixed evenly, and then reacted at 150 °C for 48 h. After the reaction is completed, 100 mL of anhydrous methanol is added, ultrasonicated for 10 min, filtered, and the solid filter cake is washed with methanol and dried to obtain 2-bromo-spiro[fluorene-9,9'-xanthene];

[0076] Step 2: Under an inert atmosphere, 0.15 g (1 mmol) of dry 1,2,4,5-tetrafluorobenzene, 0.41 g (1 mmol) of dry 2-bromo-spiro[fluorene-9,9'-xanthene], 0.28 g (2 mmol) of potassium carbonate, 0.01 g (0.05 mmol) of palladium acetate, and 0.02 g (0.1 mmol) of di-tert-butylmethylphosphonium tetrafluoroborate are dissolved in 5 mL of dry N,N-dimethylacetamide, mixed evenly, and then reacted at 105 °C for 24 h. After the reaction is completed, the system is poured into 100 mL of a saturated disodium ethylenediaminetetraacetate solution with a pH of 8 for quenching, and extracted with dichloromethane multiple times, 45 mL of dichloromethane is taken each time, the organic phases are combined, the obtained organic phase is dried with anhydrous sodium sulfate for 24 h, filtered, the solvent is removed by reduced pressure distillation, and column chromatography separation is carried out using petroleum ether and ethyl acetate with a volume ratio of 19:1 as the eluent to obtain the organic hole transporting material, and the structure is as follows:

[0077]

[0078] The yield is 77.9%.

[0079] Example 2

[0080] This example provides an organic hole transporting material, and the specific preparation process is as follows:

[0081] Step 1: Under an inert atmosphere, 1 g (3.86 mmol) of dry 2-bromofluorone, 1 ml (15.44 mmol) of methanesulfonic acid, and 4.33 g (38.6 mmol) of 4-fluorophenol were mixed evenly, and then reacted at 150 °C for 48 h. After the reaction was completed, 100 mL of anhydrous methanol was added. After ultrasonic treatment for 10 min, filtration was carried out. The solid filtrate was washed with methanol and dried to obtain 2-bromo-3',6'-difluorospiro[fluorene-9,9'-xanthene];

[0082] Step 2: Under an inert atmosphere, 0.15 g (1 mmol) of dry 1,2,4,5-tetrafluorobenzene, 0.45 g (1 mmol) of dry 2-bromo-3',6'-difluorospiro[fluorene-9,9'-xanthene], 0.28 g (2 mmol) of potassium carbonate, 0.01 g (0.05 mmol) of palladium acetate, and 0.02 g (0.1 mmol) of di-tert-butylmethylphosphonium tetrafluoroborate were dissolved in 5 mL of dry N,N-dimethylacetamide. After mixing evenly, the reaction was carried out at 105 °C for 24 h. After the reaction was completed, the system was poured into 100 mL of a saturated disodium ethylenediaminetetraacetate solution with a pH of 7.5 for quenching. Dichloromethane was used for extraction multiple times, 45 mL of dichloromethane was taken each time, and the organic phases were combined. The obtained organic phase was dried with anhydrous sodium sulfate for 24 h, filtered, the solvent was removed by distillation under reduced pressure, and column chromatography separation was carried out using petroleum ether and ethyl acetate with a volume ratio of 18:1 as the eluent to obtain an organic hole transporting material, and the structure is as follows:

[0083]

[0084] The yield was 62.5%.

[0085] Example 3

[0086] This example provides an organic hole transporting material, and the specific preparation process is as follows:

[0087] Step 1: Under an inert atmosphere, 1 g (3.86 mmol) of dry 2-bromofluorone, 1 ml (15.44 mmol) of methanesulfonic acid, and 4.33 g (38.6 mmol) of 3-fluorophenol were mixed evenly, and then reacted at 150 °C for 48 h. After the reaction was completed, 100 mL of anhydrous methanol was added. After ultrasonic treatment for 10 min, filtration was carried out. The solid filtrate was washed with methanol and dried to obtain 2-bromo-2',7'-difluorospiro[fluorene-9,9'-xanthene];

[0088] Step 2: Under an inert atmosphere, dissolve 0.15 g (1 mmol) of dried 1,2,4,5-tetrafluorobenzene, 0.45 g (1 mmol) of dried 2-bromo-2',7'-difluorospiro[fluorene-9,9'-xanthene], 0.28 g (2 mmol) of potassium carbonate, 0.01 g (0.05 mmol) of palladium acetate, and 0.02 g (0.1 mmol) of di-tert-butylmethylphosphonium tetrafluoroborate in 5 mL of dried N,N-dimethylacetamide. After mixing evenly, react at 105 °C for 24 h. After the reaction is completed, pour the system into 100 mL of a saturated disodium ethylenediaminetetraacetate solution with a pH of 8 for quenching. Extract with dichloromethane multiple times, each time taking 45 mL of dichloromethane. Combine the organic phases. Dry the obtained organic phase with anhydrous sodium sulfate for 24 h, filter, distill off the solvent under reduced pressure, and perform column chromatography separation using petroleum ether and ethyl acetate with a volume ratio of 21:1 as the eluent to obtain an organic hole transport material with the following structure:

[0089]

[0090] The yield is 53.4%.

[0091] Example 4

[0092] This example provides an organic hole transport material, and the specific preparation process is as follows:

[0093] Compared with Example 2, in this example, 4-fluorophenol is replaced with 2-fluorophenol to obtain an organic hole transport material with the following structure:

[0094]

[0095] The yield is 51.7%

[0096] Comparative Example 1

[0097] The difference between this comparative example and Example 1 is that 1,2,4,5-tetrafluorobenzene is replaced with an equimolar amount of 9,10-dibromoanthracene, and other components and preparation processes remain unchanged to obtain an organic hole transport material with the following structure:

[0098]

[0099] The yield is 47.9%.

[0100] Test Example 1

[0101] Use the organic hole transport material obtained in Example 1 to prepare a perovskite solar cell, and the specific content is as follows:

[0102] S1. After drying the clean conductive glass, immerse it successively in ultrapure water, acetone, and isopropanol, and clean it by ultrasonic cleaning for 30 min respectively. Then dry it with nitrogen gas at a gas flow rate of 0.04 L / min, and after drying, treat it with ultraviolet-ozone for 25 min to obtain the conductive glass base layer;

[0103] S2. Place the titanium tetrachloride solution on the conductive glass base layer, dry it at 70 °C for 1.5 h, rinse it with ultrapure water, and then dry it with nitrogen gas at a gas flow rate of 0.05 L / min. After drying, anneal it at 180 °C for 30 min to obtain a titanium dioxide layer with a thickness of 40 nm;

[0104] S3. Treat the conductive glass substrate with the deposited titanium dioxide layer with ultraviolet-ozone for 15 min. At the same time, mix 2 g of lead iodide, 1.5 g of 1H-imidazol-1-yl(2-methyl-3-furyl)methanone, and 0.4 g of methylammonium iodide evenly, and dissolve them in 50 mL of a mixed solution of anhydrous N,N-dimethylformamide and anhydrous dimethyl sulfoxide with a volume ratio of 4:1 to obtain a precursor solution. Drop 50 mL of the precursor solution evenly on the prepared dense titanium dioxide layer, spin-coat it at a speed of 1000 rpm for 5 s and then adjust to a speed of 4000 rpm, spin-coat it for 10 s, and then quickly drop 150 mL of chlorobenzene solution on its surface and spin-coat it again for 30 s; after spin-coating, place the conductive glass substrate on a hot plate, set the temperature to 150 °C and anneal it for 30 min to obtain a perovskite layer;

[0105] S4. Dissolve 0.3 g of the organic hole transport material in 10 mL of chlorobenzene, add 0.45 g of 4-tert-butylpyridine and 0.4 g of lithium bis(trifluoromethanesulfonyl)imide to it, mix them evenly and coat them on the perovskite layer at a spin-coating speed of 4000 rpm to obtain a hole transport layer, where the concentration of the organic hole transport material solution is 30 mg / mL;

[0106] S5. Deposit gold on the surface of the hole transport layer by thermal evaporation deposition with a thickness of 100 nm to obtain a perovskite solar cell.

[0107] Test Example 2

[0108] Use the organic hole transport material obtained in Example 1 to prepare a perovskite solar cell. Among them, in S4, dissolve 0.45 g of the organic hole transport material in 10 mL of chlorobenzene, add 0.7 g of 4-tert-butylpyridine and 0.5 g of lithium bis(trifluoromethanesulfonyl)imide to it, mix them evenly and coat them on the perovskite layer at a spin-coating speed of 4000 rpm to obtain a hole transport layer, where the concentration of the organic hole transport material solution in Example 1 is 45 mg / mL; other preparation processes are the same as those in Test Example 1 and will not be elaborated here.

[0109] Test Example 3

[0110] The perovskite solar cell was prepared using the organic hole transporting material obtained in Example 1. Among them, in step S4, 0.6 g of the organic hole transporting material was dissolved in 10 mL of chlorobenzene, 0.9 g of 4-tert-butylpyridine and 1 g of lithium bis(trifluoromethanesulfonyl)imide were added thereto, and after mixing evenly, it was spin-coated on the perovskite layer at a spin-coating speed of 4000 rpm to obtain a hole transporting layer, wherein the concentration of the organic hole transporting material solution in Example 1 was 60 mg / mL; the other preparation processes were the same as those in Test Example 1 and will not be elaborated here.

[0111] Test Example 4

[0112] The organic hole transporting material obtained in Example 2 was used to replace the organic hole transporting material obtained in Test Example 1 for preparing the perovskite solar cell. Among them, the concentration of the organic hole transporting material solution in Example 2 was 30 mg / mL, and the specific preparation process was the same as that in Test Example 1 and will not be elaborated here.

[0113] Test Example 5

[0114] The organic hole transporting material obtained in Example 2 was used to replace the organic hole transporting material obtained in Test Example 1 for preparing the perovskite solar cell. Among them, in step S4, 0.45 g of the organic hole transporting material was dissolved in 10 mL of chlorobenzene, 0.7 g of 4-tert-butylpyridine and 0.5 g of lithium bis(trifluoromethanesulfonyl)imide were added thereto, and after mixing evenly, it was spin-coated on the perovskite layer at a spin-coating speed of 4000 rpm to obtain a hole transporting layer, wherein the concentration of the organic hole transporting material solution in Example 2 was 45 mg / mL; the other preparation processes were the same as those in Test Example 1 and will not be elaborated here.

[0115] Test Example 6

[0116] The organic hole transporting material obtained in Example 2 was used to replace the organic hole transporting material obtained in Test Example 1 for preparing the perovskite solar cell. Among them, in step S4, 0.6 g of the organic hole transporting material was dissolved in 10 mL of chlorobenzene, 0.9 g of 4-tert-butylpyridine and 1 g of lithium bis(trifluoromethanesulfonyl)imide were added thereto, and after mixing evenly, it was spin-coated on the perovskite layer at a spin-coating speed of 4000 rpm to obtain a hole transporting layer, wherein the concentration of the organic hole transporting material solution in Example 2 was 60 mg / mL, and the other preparation processes were the same as those in Test Example 1 and will not be elaborated here.

[0117] Test Example 7

[0118] The organic hole transporting material obtained in Example 3 was used to replace the organic hole transporting material obtained in Test Example 1 for preparing the perovskite solar cell. Among them, the concentration of the organic hole transporting material solution in Example 3 was 30 mg / mL, and the specific preparation process was the same as that in Test Example 1 and will not be elaborated here.

[0119] Test Example 8

[0120] The organic hole transporting material obtained in Example 3 was used to replace the organic hole transporting material obtained in Test Example 1 for the preparation of perovskite solar cells. In step S4, 0.45 g of the organic hole transporting material was dissolved in 10 mL of chlorobenzene, 0.7 g of 4-tert-butylpyridine and 0.5 g of lithium bis(trifluoromethanesulfonyl)imide were added thereto, and after mixing evenly, it was spin-coated on the perovskite layer at a spin-coating speed of 4000 rpm to obtain a hole transporting layer. The concentration of the organic hole transporting material solution in Example 3 was 45 mg / mL. The specific preparation process was the same as that in Test Example 1 and will not be described herein again.

[0121] Test Example 9

[0122] The organic hole transporting material obtained in Example 3 was used to replace the organic hole transporting material obtained in Test Example 1 for the preparation of perovskite solar cells. In step S4, 0.6 g of the organic hole transporting material was dissolved in 10 mL of chlorobenzene, 0.9 g of 4-tert-butylpyridine and 1 g of lithium bis(trifluoromethanesulfonyl)imide were added thereto, and after mixing evenly, it was spin-coated on the perovskite layer at a spin-coating speed of 4000 rpm to obtain a hole transporting layer. The concentration of the organic hole transporting material solution in Example 3 was 60 mg / mL. The specific preparation process was the same as that in Test Example 1 and will not be described herein again.

[0123] Test Example 10

[0124] The organic hole transporting material obtained in Example 4 was used to replace the organic hole transporting material obtained in Test Example 1 for the preparation of perovskite solar cells. The concentration of the organic hole transporting material solution in Example 4 was 30 mg / mL. The specific preparation process was the same as that in Test Example 1 and will not be described herein again.

[0125] Test Example 11

[0126] The organic hole transporting material obtained in Example 4 was used to replace the organic hole transporting material obtained in Test Example 1 for the preparation of perovskite solar cells. In step S4, 0.45 g of the organic hole transporting material was dissolved in 10 mL of chlorobenzene, 0.7 g of 4-tert-butylpyridine and 0.5 g of lithium bis(trifluoromethanesulfonyl)imide were added thereto, and after mixing evenly, it was spin-coated on the perovskite layer at a spin-coating speed of 4000 rpm to obtain a hole transporting layer. The concentration of the organic hole transporting material solution in Example 4 was 45 mg / mL. The specific preparation process was the same as that in Test Example 1 and will not be described herein again.

[0127] Test Example 12

[0128] Replace the organic hole transport material obtained in Example 4 with the organic hole transport material obtained in Test Example 1 for the preparation of a perovskite solar cell. Among them, in S4, dissolve 0.6 g of the organic hole transport material in 10 mL of chlorobenzene, add 0.9 g of 4-tert-butylpyridine and 1 g of lithium bis(trifluoromethanesulfonyl)imide thereto, and after mixing evenly, coat it on the perovskite layer at a spin coating speed of 4000 rpm to obtain a hole transport layer. The concentration of the organic hole transport material solution in Example 4 is 60 mg / mL. The specific preparation process is the same as that in Test Example 1 and will not be elaborated here.

[0129] Test Example 13

[0130] Use commercially available Spiro-OMeTAD to replace the sample obtained in Example 1 as the hole transport material to prepare a perovskite solar cell. The specific preparation process is the same as that in Test Example 1 and will not be elaborated here.

[0131] Test Example 14

[0132] Replace the organic hole transport material obtained in Comparative Example 1 with the organic hole transport material obtained in Test Example 1 for the preparation of a perovskite solar cell. The concentration of the organic hole transport material solution in Comparative Example 1 is 30 mg / mL. The specific preparation process is the same as that in Test Example 1 and will not be elaborated here.

[0133] Test Example 15

[0134] Replace the organic hole transport material obtained in Comparative Example 1 with the organic hole transport material obtained in Test Example 1 for the preparation of a perovskite solar cell. Among them, in S4, dissolve 0.45 g of the organic hole transport material in 10 mL of chlorobenzene, add 0.7 g of 4-tert-butylpyridine and 0.5 g of lithium bis(trifluoromethanesulfonyl)imide thereto, and after mixing evenly, coat it on the perovskite layer at a spin coating speed of 4000 rpm to obtain a hole transport layer. The concentration of the organic hole transport material solution in Comparative Example 1 is 45 mg / mL. The specific preparation process is the same as that in Test Example 1 and will not be elaborated here.

[0135] Test Example 16

[0136] Replace the organic hole transport material obtained in Comparative Example 1 with the organic hole transport material obtained in Test Example 1 for the preparation of a perovskite solar cell. Among them, in S4, dissolve 0.6 g of the organic hole transport material in 10 mL of chlorobenzene, add 0.9 g of 4-tert-butylpyridine and 1 g of lithium bis(trifluoromethanesulfonyl)imide thereto, and after mixing evenly, coat it on the perovskite layer at a spin coating speed of 4000 rpm to obtain a hole transport layer. The concentration of the organic hole transport material solution in Comparative Example 1 is 60 mg / mL. The specific preparation process is the same as that in Test Example 1 and will not be elaborated here.

[0137] Test Results

[0138] The battery performance data of each test example are shown in Table 1.

[0139] Table 1 Performance data table of perovskite solar cells prepared in each test example

[0140]

[0141]

[0142] As can be seen from Table 1, the organic hole transport material provided by the present invention can exhibit optoelectronic properties relatively close to those obtained with the Sprio-OMeTAD material. In particular, the battery device obtained in Test Example 5 is closest in performance to the battery device prepared with the Sprio-OMeTAD material. However, compared with the Sprio-OMeTAD material, the organic hole transport material prepared by the present invention has the advantages of low raw material prices, simpler synthesis methods, fewer synthesis steps, and easier purification, can meet commercial applications, and exhibits greater cost advantages in large-scale production.

[0143] According to Figure 3 and Figure 4 it can be seen that the thermal decomposition temperature of the organic hole transport material obtained in Example 2 at a weight loss of 5% is 416 °C, which also exceeds 400 °C, indicating that the material has good thermal stability and can well meet the basic requirements as a hole material. Secondly, it is worth mentioning that the organic hole transport material obtained in Example 2 has no obvious endothermic or exothermic process within a temperature of 100 °C, indicating that the material has good anti-crystallization stability, is higher than the glass transition temperature of general hole transport materials, and has good thermal stability.

[0144] Using Table 1 and the energy level calculation formula (E HOMO = -(Eox + 4.4) eV, where Eox is the starting potential), it can be obtained that the HOMO energy level of the organic hole transport material obtained in Example 2 is -5.27 eV, and the LUMO energy level is -2.31 eV. The energy levels are very close to those of the perovskite layer, which can not only transport holes but also effectively block the passage of electrons, indicating that introducing fluorine atoms with electron-withdrawing properties into the molecular structure can indeed reduce the HOMO energy level of the compound. Reducing the energy gap between the HOMO energy level of the hole transport material and the maximum valence band of perovskite is beneficial to improving the open-circuit voltage and hole extraction, so the fluorinated product may obtain a higher open-circuit voltage. Furthermore, a higher device efficiency can be obtained.

[0145] Example 4 After fabricating the device, the space charge limited current method was used to test the device. The hole mobility of the compound was tested using the space charge limited current method (SCLC). The hole mobility test characterizes the hole transport ability of the compound. The higher the hole mobility, the better the hole transport ability. The calculated hole mobility of the organic hole transport material obtained in Example 2 was 2.31×10 -4 cm 2 V -1 S -1 。

[0146] In summary, the present invention designed and synthesized a class of organic hole transport materials. A simple synthesis method of direct arylation was adopted, and a simple column chromatography method could be used to directly purify the product with high purity. The central carbon atom of the spirofluorene molecule was sp 3 hybridized. Therefore, the spatial structure of the spirofluorene molecule showed a non-planar state, which could reduce the formation of material aggregates to a certain extent and avoid the quenching of material luminescence. At the same time, the reduction of molecular packing also made the material have good solubility. Therefore, a hole transport layer with better film-forming properties could be obtained, reducing many defects of fluorene-based materials. At the same time, the thermal stability of the hole transport material could be improved, thereby improving the stability of the device. The fluorene structure and the inherent properties of fluorobenzene made the molecule have relatively good thermodynamic properties and stable spectral properties, and finally an organic hole transport material with excellent device performance and good stability was obtained.

[0147] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A perovskite solar cell, characterized in that: It includes a hole transport layer; wherein the material of the hole transport layer is an organic hole transport material, and its structure is shown in Formula 1: Formula 1 R1, R2, and R3 are selected from H or F, wherein R1, R2, and R3 have at least two hydrogen atoms.

2. The perovskite solar cell according to claim 1, wherein: The structure of the organic hole transport material is , or any one of them 3. The perovskite solar cell according to claim 1, wherein: The preparation method of the organic hole transport material comprises at least the following steps: in an inert atmosphere, 1,2,4,5-tetrafluorobenzene, the spirofluorene xanthene derivative shown in Formula 2, an acid binding agent, a palladium catalyst and a phosphorus-containing ligand are subjected to a Suzuki coupling reaction in an organic solvent to obtain the organic hole transport material; Among them, the structure of formula 2 is as follows: Formula 2 R1 and R2 are selected from H or F, wherein R1 and R2 have at least one hydrogen atom.

4. The perovskite solar cell according to claim 3, wherein: The spirofluorene xanthene derivative is , or any one of; and / or The phosphorus-containing ligand is any one of di-tert-butyl methylphosphine tetrafluoroborate, 2-dicyclohexylphosphine-2',4',6'-triisopropylbiphenyl, tri-tert-butylphosphine, 1,1'-binaphthyl-2,2'-bisdiphenylphosphine, tri(o-methylphenyl)phosphine or 4,5-bisdiphenylphosphine-9,9-dimethylxanthene; and / or The acid binding agent is any one of calcium carbonate, cesium carbonate, sodium carbonate, potassium phosphate, potassium tert-butoxide or sodium tert-butoxide; and / or The palladium catalyst is any one of tetrakis(triphenylphosphine)palladium, [1,1-bis(diphenylphosphino)ferrocene]palladium dichloride or palladium acetate; and / or The molar ratio of the spirofluorene xanthene derivative to 1,2,4,5-tetrafluorobenzene is 1:1-1.2; and / or The molar ratio of the spirofluorene xanthene derivative to the palladium catalyst is 5-50:1; and / or The molar ratio of the spirofluorene xanthene derivative to the acid binding agent is 1:2-10; and / or The molar ratio of the spirofluorene xanthene derivative to the phosphorus-containing ligand is 1:5-10.

5. The perovskite solar cell according to any one of claims 3 or 4, characterized in that: The preparation method of the spirofluorene xanthene derivative comprises the following steps: Under an inert atmosphere, 2-bromofluorenone, methanesulfonic acid and a phenolic ligand are uniformly mixed, and then dehydration condensation reaction is carried out in an organic solvent to obtain a spirofluorene xanthene derivative.

6. The perovskite solar cell according to claim 5, wherein: The phenolic ligand is any one of phenol, 4-fluorophenol or 3-fluorophenol; and / or The molar ratio of the 2-bromofluorenone, methanesulfonic acid and phenolic ligand is 1-1.1:4-5:10-12.

7. The perovskite solar cell according to claim 1, wherein: The preparation method of the hole transport layer comprises the following steps: dissolving the organic hole transport material in chlorobenzene to obtain an organic hole transport material solution, adding 4-tert-butylpyridine and lithium bis(trifluoromethanesulfonyl)imide to the organic hole transport material solution, mixing evenly and then spin coating the mixture onto the perovskite layer to obtain the hole transport layer.

8. The perovskite solar cell according to claim 7, wherein: The mass ratio of the organic hole transport material, 4-tert-butylpyridine and lithium bis(trifluoromethanesulfonyl)imide is 1-2:1.5-3.5:1.2-3; and / or The concentration of the organic hole transport material solution is 30 mg / mL-60 mg / mL.

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