Triphenylamine organic small molecule compound, preparation method and application of triphenylamine organic small molecule compound in perovskite solar cell

Abstract

The invention discloses a triphenylamine organic small molecule compound, a preparation method and application of the triphenylamine organic small molecule compound in a perovskite solar cell. As a molecular passivator interacting with a perovskite material, the small molecular compound can accurately and efficiently passivate grain boundary or surface defects of various perovskite components; the preparation process and conditions are relatively simple, and the method is suitable for large-scale industrial preparation; when the perovskite thin film is applied to the perovskite solar cell, the defects of the perovskite thin film are effectively improved, Pb < 2 + > ions are firmly coordinated, crystal defects are synergistically passivated, charge recombination is reduced, and the efficiency and stability of the perovskite solar cell are improved.

Description

Technical Field

[0001] The present invention relates to an organic small molecule compound, in particular to a triphenylamine-based organic small molecule compound, and also relates to a preparation method of the above triphenylamine-based organic small molecule compound and its application in perovskite solar cells. Background Art

[0002] Perovskite solar cells (PSCs) have attracted extensive attention in the photovoltaic field due to their high power conversion efficiency (PCE) and simple fabrication process. Compared with traditional crystalline silicon cells, perovskite solar cells have advantages such as adjustable bandgap, high carrier mobility, and simple manufacturing process, showing great commercial potential. Although the power conversion efficiency of perovskite solar cells has exceeded 26%, their long-term stability remains the main obstacle restricting commercialization. The multilayer structure characteristics of perovskite solar cells lead to various defects easily generated on the surface, bulk, and grain boundaries of the light absorption layer, such as film defects, ion migration, and phase separation. These defects can cause non-radiative recombination and hinder the formation of highly crystalline perovskite films. Under continuous illumination, perovskite may undergo phase segregation, resulting in the appearance of pinholes and Pb 2+ ion precipitation, seriously affecting the power conversion efficiency and stability of the device.

[0003] To solve these problems, researchers have improved the performance of the device by defect passivation, molecular additives, optimizing perovskite components, and improving the fabrication process, etc. In particular, molecular additive passivation has been proven to be effective in reducing the recombination loss of photo-generated electrons and holes, and enhancing the open-circuit voltage (V OC ) and power conversion efficiency of perovskite devices; passivators (such as small molecules, polymers, ionic compounds, etc.) can passivate positively or negatively charged defects through mechanisms such as Lewis acid-base interaction, ionic bond, and hydrogen bond. Therefore, developing a molecular passivator that can interact with perovskite materials is crucial for precisely and efficiently passivating the grain boundary or surface defects of various perovskite components. Summary of the Invention

[0004] Object of the Invention: The object of the present invention is to provide a triphenylamine-based organic small molecule compound, and also provide a preparation method of the above compound and its application as a molecular additive in perovskite solar cells, to form a highly crystalline perovskite film, reduce the surface defects of the perovskite film, and inhibit the non-radiative recombination of carriers, thereby improving the power conversion efficiency and stability of the device.

[0005] Technical Solution: The present invention discloses a triphenylamine-based organic small molecule compound, and the structure of the compound is shown in Formula I:

[0006]

[0007] The preparation method of the above triphenylamine-based organic small molecule compound comprises the following steps:

[0008] (1) Dissolve 4-(trifluoromethyl)aniline and p-iodophenol in o-xylene under the condition of a catalyst, heat up the reaction, extract, dry, and purify by column chromatography to obtain compound A;

[0009] (2) Mix compound A, N,N-dimethylformamide, sodium hydroxide, and chloroacetaldehyde, react, extract, dry, and purify by column chromatography to obtain the triphenylamine-based organic small molecule compound;

[0010] Among them, the structural formula of compound A is:

[0011] Among them, the synthesis reaction equation is as follows:

[0012]

[0013] Among them, in step (1), the catalyst Pd 2 (dba) 3 , t-BuOK and P(t-Bu) 3 HBF 4 , and the heat-up reaction is a reaction in an oil bath at 110-120 °C in a nitrogen environment.

[0014] Among them, the volume-mass ratio of 4-(trifluoromethyl)aniline, p-iodophenol, and o-xylene is 1 g: 3 g: 50-80 mL, preferably 1 g: 3 g: 60 mL.

[0015] Among them, the mass ratio of the catalyst Pd 2 (dba) 3 , t-BuOK and P(t-Bu) 3 HBF 4 to 4-(trifluoromethyl)aniline is 1: 10-15: 1: 1-5, preferably 1: 12: 1: 5.

[0016] Among them, in step (2), the mass ratio of compound A, sodium hydroxide, N,N-dimethylformamide, and chloroacetaldehyde is 1-5 g: 1 g: 50-60 mL: 6-7 g; step (2) specifically is to carry out the reaction at room temperature, mix compound A, N,N-dimethylformamide, and sodium hydroxide and let it stand for 1-1.5 hours, and then add chloroacetaldehyde to the solution and stir at room temperature for 12-14 hours; after the reaction is completed, extract with dichloromethane and water, and vacuum dry and filter with Na 2 SO 4 .

[0017] Among them, the mass-volume ratio of compound A, sodium hydroxide and DMF is 1-5 g: 1 g: 50-60 mL, preferably 3.5 g: 1 g: 58 mL.

[0018] Among them, the mass-volume ratio of chloroacetaldehyde and DMF is 1 g: 5-10 mL, preferably 1 g: 9 mL.

[0019] The present invention also discloses the application of the above triphenylamine-based organic small molecule compound in a perovskite solar cell, and the triphenylamine-based organic small molecule compound is prepared into a perovskite precursor solution for the preparation of a perovskite solar cell.

[0020] Among them, the perovskite precursor solution includes perovskite raw materials and a triphenylamine-based organic small molecule compound as an additive, and the perovskite raw materials include FAI, PbI 2 , CsI, MABr, PbBr and MACl.

[0021] Among them, in the perovskite precursor solution, the mass ratio of FAI, PbI 2 , CsI, MABr, PbBr, MACl and the triphenylamine-based organic small molecule compound is 294.1: 889.6: 23.4: 1: 1.9: 36.5: 2-10.

[0022] Among them, for the perovskite solar cell, its preparation method is to spin-coat NiO on a transparent conductive oxide substrate x to prepare a hole transport layer, spin-coat the perovskite precursor solution on the NiO X layer, anneal to obtain a perovskite light absorption layer; then sequentially prepare an electron transport layer, a blocking layer and a metal top electrode to obtain the perovskite solar cell.

[0023] Among them, the spin-coating parameters are set to 2000-3000 rpm, spin-coat for 10 s, then 4000-5000 rpm, spin-coat for 30 s, and add chlorobenzene as an anti-solvent 15-10 s before the end; the spin-coating parameter setting is preferably 2500 rpm, spin-coat for 10 s, then 5000 rpm, spin-coat for 30 s, and add chlorobenzene as an anti-solvent 13 s before the end.

[0024] Among them, the annealing temperature is 100 °C-120 °C, and the time is 10-20 min; the annealing conditions are preferably 100 °C and 15 min.

[0025] Among them, the transparent conductive oxide substrate is indium-doped tin oxide (ITO) conductive glass.

[0026] Among them, the transparent conductive oxide substrate needs to be ultrasonically cleaned with detergent, deionized water, acetone, and isopropanol for 20 min in sequence before preparing the perovskite solar cell, and dried with nitrogen, and then the surface of the substrate is treated with an ultraviolet lamp.

[0027] Among them, the preparation of the perovskite light absorption layer includes: weighing a certain amount of FAI, PbI 2 , CsI, MABr, PbBr, and MACl to prepare a perovskite precursor solution with a concentration of 1.8M FA 0.95 Cs 0.05 PbI 3 Then, 2 mg to 10 mg of triphenylamine organic molecular additive is dissolved in the perovskite precursor solution, and the perovskite precursor solution is spin-coated on the hole transport layer, and then annealed at 100 °C on a heating table for 15 min, and finally a perovskite light absorption layer is formed.

[0028] Among them, the electron transport layer is prepared by high-vacuum evaporation. C 60 (20 nm) and BCP (5 - 8 nm) are evaporated on the surface of the perovskite light absorption layer to obtain an electron transport layer and a blocking layer.

[0029] Among them, the top electrode is prepared by high-vacuum evaporation. Under the condition of a vacuum degree of 5×10 -4 Pa, a metal top electrode is evaporated to finally prepare a perovskite solar cell. One of gold, silver, and copper is selected as the material, and the thickness is set to 100 nm.

[0030] Principle of the invention: The triphenylamine-based organic small molecule compound of the present invention, as a molecular passivator interacting with the perovskite material, can accurately and efficiently passivate the grain boundaries or surface defects of various perovskite components. The O atom of C=O and the -CF 3 functional group in the small molecule additive can interact with the uncoordinated Pb 2+ in the perovskite to form strong coordination bonds, synergistically passivate crystal defects, thereby improving the crystallization and stability of the perovskite film; the F atom can form strong hydrogen bonds with the FA cation, which can effectively hinder the crystallization of the perovskite and promote the formation of a high-quality perovskite film, improving the performance of the device; the strong hydrophobicity of the -CF 3 functional group itself enables the perovskite film to form a hydrophobic barrier, thereby improving the stability of the device. Therefore, by introducing the triphenylamine organic small molecule additive, many crystal defects (including anion vacancies and insufficiently coordinated cations) that usually occur during the dissolution process of the perovskite film are improved, the defect density is reduced, thereby regulating the morphology of the perovskite, passivating the defects at the surface and grain boundaries, inhibiting non-radiative recombination, and improving the photoelectric conversion efficiency and stability of the perovskite solar cell.

[0031] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: (1) The triphenylamine-based organic small molecule compound of the present invention, as a passivator in perovskite solar cells, effectively promotes charge transport at the perovskite / transport layer interface, while improving the quality and hydrophobicity of the perovskite film, thereby enhancing the device performance and stability of perovskite solar cells; (2) The preparation process and conditions of the triphenylamine-based organic small molecule compound of the present invention are relatively simple and suitable for large-scale industrial production. Description of the Drawings

[0032] Figure 1 It is a schematic structural diagram of the triphenylamine-based organic small molecule of the present invention;

[0033] Figure 2 It is a synthesis flow chart of the triphenylamine-based organic small molecule of the present invention;

[0034] Figure 3 It is a schematic structural diagram of the p-i-n type perovskite solar cell of the present invention;

[0035] Figure 4 It is the J-V curve of the devices in Example 2 and Comparative Example 1. Detailed Embodiments

[0036] The technical solutions of the present invention will be further described below in conjunction with the embodiments. The test materials used in the embodiments can be obtained through conventional channels.

[0037] Example 1

[0038] The synthesis route of the triphenylamine-based organic small molecule compound of the present invention is as follows:

[0039]

[0040] The specific steps include:

[0041] (1) Add 4-aminobenzotrifluoride (2.5 g), p-iodophenol (7.59 g), Pd 2 (dba) 3 (0.48 g), t-BuOK (6 g) and P(t-Bu) 3 HBF 4 (0.5 g) into a 150 mL schlenk flask. Then add 60 mL of o-xylene. After evacuating three times, react under a nitrogen atmosphere. Heat up to 110 °C and react overnight. Add water to the mixture and then extract with dichloromethane. Dry the organic layer with Na 2 SO 4 and concentrate under vacuum. The crude product is purified by silica gel column chromatography (dichloromethane / petroleum ether 1 / 8) to obtain compound A.

[0042] (2) At room temperature, sodium hydride (0.86 g) was added to a DMF (50 mL) solution of the intermediate, and the mixture was allowed to stand for 1 hour. Then, chloroacetaldehyde (5.45 g) was added to the solution and the mixture was stirred for 12 hours. After the reaction was completed, water was added to quench the reaction, and the reaction mixture was extracted with dichloromethane and water. The organic layer was dried under vacuum with Na 2 SO 4 and filtered; the product was separated by silica gel column chromatography, eluted with petroleum ether: ethyl acetate (15:1), to obtain a triphenylamine-based organic small molecule compound.

[0043] The prepared triphenylamine-based organic small molecule compound is composed of triphenylamine connecting two symmetric carboxyl groups and -CF 3 functional groups. When it is applied to the perovskite precursor solution as a molecular additive, due to its special symmetric structure, the O atom of C=O in the carboxyl group, and the -CF 3 functional groups in the small molecule can interact with the uncoordinated Pb 2+ in the perovskite to form strong coordination bonds, synergistically passivating crystal defects, thereby improving the crystallization and stability of the perovskite film; F atoms can form strong hydrogen bonds with FA cations, which can effectively hinder the crystallization of perovskite and promote the formation of high-quality perovskite films, improving the performance of the device; the strong hydrophobicity of the -CF 3 functional group itself enables the perovskite film to form a hydrophobic barrier, thereby improving the stability of the device.

[0044] Example 2

[0045] The triphenylamine-based organic small molecule compound of the present invention is used as a passivator in the preparation of perovskite solar cells, which specifically includes the following steps:

[0046] S1: Take a transparent conductive ITO substrate with an area of 1.5 * 1.5 cm 2 , and ultrasonically clean it with detergent, deionized water, acetone, and isopropanol for 20 min respectively. Then, dry the ITO substrate with nitrogen, and finally perform surface treatment on the ITO substrate with an ultraviolet lamp.

[0047] S2: Preparation of the hole transport layer. NiO x was configured into a precursor solution with a concentration of 10 mg / mL, and the solvent was deionized water. After magnetic stirring for 30 min, it was filtered with a PTEE filter head for standby; use a pipette to uniformly coat NiO x on the ITO surface by spin coating, set the spin coating speed to 1500 rpm, and the time to 30 s; after spin coating, anneal it on a heating table at 150 °C for 10 min.

[0048] S3: Preparation of the perovskite precursor solution. Weigh 294.1 mg of FAI, 889.6 mg of PbI2 , 23.4 mg of CsI, 1 mg of MABr, 1.9 mg of PbBr, 36.5 mg of MACl and 4 mg of the above synthesized triphenylamine-based organic small molecule are dissolved in a solution of 800 μl of DMF and 200 μl of DMSO, and magnetically stirred for more than 6 h to prepare a 1.8 M FA 0.95 Cs 0.05 PbI 3 perovskite precursor solution, which is filtered with a PTEE filter head for standby.

[0049] S4: Preparation of the perovskite layer. Use a pipette to aspirate 80 μl of the 1.8 M FA 0.95 Cs 0.05 PbI 3 perovskite precursor solution and evenly cover it on the ITO / NiO x layer for spin coating. The spin coating parameters are first set to 2500 rpm for 10 s, then continuously spin coated, the spin coating speed is set to 5000 rpm, and the time is set to 30 s. And 100 μl of chlorobenzene is dropped on the substrate as an anti-solvent 13 s before the end of spin coating. After spin coating, anneal at 100 °C on a hot plate for 15 min.

[0050] S5: Deposition of the electron transport layer and the blocking layer. Place the substrate after the above treatment in an ultra-high vacuum evaporation chamber in a glove box, and sequentially evaporate 20 nm thick C 60 and 8 nm thick BCP.

[0051] S6: Deposition of the metal electrode. Transfer the substrate deposited with C 60 and BCP to the metal evaporation chamber, and thermally evaporate a 100 nm thick Ag film under ultra-high vacuum.

[0052] Example 3

[0053] This example provides a perovskite solar cell, and the specific cell structure is ITO / NiO x / perovskite layer / C 60 / BCP / Ag. The difference from Example 2 is only that the addition amount of the small molecule in step 3 is 2 mg, and other parameters remain unchanged.

[0054] Example 4

[0055] This example provides a perovskite solar cell, and the specific cell structure is ITO / NiO x / perovskite layer / C 60 / BCP / Ag. The difference from Example 2 is only that the addition amount of the small molecule in step 3 is 6 mg, and other parameters remain unchanged. The specific implementation steps of step 3 are as follows:

[0056] Example 5

[0057] This embodiment provides a perovskite solar cell, and the specific cell structure is ITO / NiO x / perovskite layer / C 60 / BCP / Ag. The difference from Example 2 is only that the addition amount of the small molecule in Step 3 is 8 mg, and other parameters remain unchanged.

[0058] Example 6

[0059] This embodiment provides a perovskite solar cell, and the specific cell structure is ITO / NiO x / perovskite layer / C 60 / BCP / Ag. The difference from Example 2 is only that the addition amount of the small molecule in Step 3 is 10 mg, and other parameters remain unchanged.

[0060] Comparative Example 1

[0061] This comparative example provides a perovskite solar cell, and the specific cell structure is ITO / NiO x / perovskite layer / C 60 / BCP / Ag. The difference from Example 2 is only that no small molecule is added in Step 3, and other parameters remain unchanged.

[0062] Performance test: The perovskite solar cells of Examples 2 to 6 and Comparative Example 1 were subjected to performance tests. Under the simulated AM1.5G spectrum, the J-V characteristic curves of the devices were measured using a Keithley 2602B light source. Using a solar simulator (Zolix SS150), the light intensity was calibrated by NREL using a standard silicon solar cell device. The effective measurement area was 0.1 cm 2 , and under reverse and forward bias scans, the step size was set to 0.02 V, and the bias range was from -0.2 V to 1.2 V.

[0063] Table 1. Performance of the perovskite solar cells of Comparative Example 1 and Examples 2 to 6

[0064] <![CDATA[V OC [V]]]> <![CDATA[J SC [mA cm 2 > FF [%] PCE [%] Comparative Example 1 1.12 21.99 78.55 19.39 Example 2 1.17 25.27 81.83 24.66 Example 3 1.14 24.44 77.08 21.54 Example 4 1.17 25.13 78.36 23.62 Example 5 1.14 24.47 78.84 22.1 Example 6 1.13 22.98 78.91 20.61

[0065] As can be seen from Table 1 and Figure 4 it can be known that by comparing the J-V curves of the devices in Comparative Example 1 and Example 2 of the present invention, the J-V curve of Example 2 has been significantly improved; when triphenylamine-based organic small molecules are applied to the perovskite precursor solution, the V of the perovskite solar cell device prepared OC 、J SC, FF is significantly improved, thus increasing the PCE value of the device. In Example 2, when the amount of the small molecule is 4 mg, the photoelectric conversion efficiency of the device is the highest. Due to its structural advantages, special symmetric structure, the O atom of C=O in the carboxyl group, and the -CF 3 functional group of the triphenylamine-based organic small molecule prepared in Example 1 of the present invention can interact with the uncoordinated Pb 2+ in the perovskite to form strong coordination bonds, synergistically passivate crystal defects, and improve device performance; when interacting with the perovskite precursor solution, the hydrophobicity of its -CF 3 functional group forms a barrier on the surface of the perovskite layer to prevent further oxidation of the device and improve the stability of the device.

[0066] Therefore, the molecular passivator of the triphenylamine-based organic small molecule compound of the present invention that interacts with the perovskite material can accurately and efficiently passivate the grain boundaries or surface defects of various perovskite components, promote charge transport at the perovskite / transport layer interface, improve the quality and hydrophobicity of the perovskite film, and further improve the performance and stability of the perovskite solar cell device.

Claims

1. A triphenylamine organic small molecule compound, characterized in that: The structure of the compound is shown in Formula I:

2. A method for preparing the triphenylamine organic small molecule compound according to claim 1, characterized in that: The following steps are involved: (1) dissolving 4-(trifluoromethyl)aniline and p-iodophenol in o-xylene under a catalyst condition, heating to react, extracting, drying, and purifying by column chromatography to obtain compound A; (2) Compound A, N,N-dimethylformamide, sodium hydroxide and chloroacetaldehyde are mixed, reacted, extracted, dried and purified by column chromatography to obtain a triphenylamine organic small molecule compound; Wherein, the structural formula of compound A is:

3. The method according to claim 2, characterized in that: In step (1), the catalysts Pd2(dba)3, t-BuOK and P(t-Bu)3HBF4, the temperature-raising reaction is a reaction at 110-120°C in an oil bath in a nitrogen environment; the volume mass ratio of 4-(trifluoromethyl)aniline, p-iodophenol and o-xylene is 1g:3g:50-80mL; the mass ratio of the catalysts Pd2(dba)3, t-BuOK and P(t-Bu)3HBF4 to 4-(trifluoromethyl)aniline is 1:10-15:1:1-5.

4. The method according to claim 2, characterized in that: In step (2), the mass volume ratio of compound A, sodium hydroxide and DMF is 1-5g:1g:50-60mL; the mass volume ratio of chloroacetaldehyde and DMF is 1g:5-10mL; step (2) specifically comprises the following steps: reacting at room temperature, mixing compound A, N,N-dimethylformamide and sodium hydroxide and standing for 1-1.5 hours, then adding chloroacetaldehyde to the solution and stirring at room temperature for 12-14 hours; after the reaction is completed, extracting with dichloromethane and water, and vacuum drying with Na2SO4 and filtering.

5. An application of the triphenylamine organic small molecule compound according to claim 1 in a perovskite solar cell, characterized in that: The triphenylamine-based organic small molecule compound is used to prepare a perovskite precursor liquid for use in the preparation of a perovskite solar cell.

6. The use according to claim 5, characterized in that: The perovskite precursor liquid comprises a perovskite raw material and a triphenylamine-based organic small molecule compound as an additive, wherein the perovskite raw material comprises FAI, PbI2, CsI, MABr, PbBr and MACl.

7. The use according to claim 6, characterized in that: The mass ratio of the perovskite precursor liquid, FAI, PbI2, CsI, MABr, PbBr, MACl and triphenylamine organic small molecule compounds is 294.1:889.6:23.4:1:1.9:36.5:2-10.

8. The use according to claim 5, characterized in that: The perovskite solar cell is prepared by spin coating NiO on a transparent conductive oxide substrate. x Prepare the hole transport layer by spin coating the perovskite precursor liquid on NiO X The layer is annealed to obtain a perovskite light absorption layer; and then an electron transport layer, a barrier layer and a metal top electrode are sequentially prepared.

9. The use according to claim 8, characterized in that: The spin coating parameters are set to 2000-3000 rpm spin coating, then 4000-5000 rpm spin coating, and chlorobenzene is added dropwise as an anti-solvent 15-10 seconds before the end.

10. The use according to claim 8, characterized in that: The annealing temperature is 100° C. to 120° C., and the annealing time is 10 to 20 minutes.

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