High-stability environment-friendly perovskite solar cell

Abstract

The application discloses a kind of high stability environmental protection type perovskite solar cell, it is to introduce a kind of passivation agent into perovskite grain boundary as photoactive layer, and by molecular structure design makes passivation agent molecule between it can pass through hydrogen bond and π effect Self-assembly forms ordered flexible porous space structure, to passivate perovskite grain boundary defect, effectively eliminates stress, and adsorbs lead ion.The perovskite solar cell device prepared by the application is improved to 23% in photoelectric conversion, the performance is stable in 1200 hours, and the leakage rate of lead is reduced by 60% after being destroyed, and it is friendly to environment.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of photoelectric functional materials and devices, and particularly relates to a high-stability environment-friendly perovskite solar cell. BACKGROUND

[0002] The photoelectric conversion efficiency of perovskite solar cells (PSCs) has increased from the initial 3.8% to more than 25.5% in the past decade, with a development speed far exceeding that of silicon-based solar cells (which took nearly 40 years to reach a comparable level), and PSCs have therefore become the most promising product to replace traditional silicon-based solar cells among the third-generation solar cells. At present, the most important problems encountered in the commercialization of PSCs are two-fold, namely, the device stability problem and the problem of toxic substance leakage caused by lead in the perovskite.

[0003] Many defects exist in the perovskite polycrystalline film prepared by a solution method, and these grain boundaries or surface defects can promote ion migration, easily become weak points for attacks by water, oxygen, light and the like, and also serve as charge recombination centers to cause hindrance to carrier transport, resulting in serious performance degradation. In order to passivate the defects, passivation agents such as organic ammonium salts, Lewis acids / bases or zwitterions are introduced into the perovskite grain boundaries, and especially some aromatic small molecules with functional sites have been proved to effectively passivate defects and improve performance and stability. Recently, it has been found that film stress caused by a heating process is also an important factor causing instability of the perovskite film, and the current solution is to introduce a material with a large thermal expansion coefficient as a stress buffer layer. However, the aromatic molecules have a large rigidity, and their narrow expansion space is insufficient to buffer the deformation at the grain boundaries. In summary, it is currently impossible to simultaneously solve the problems of defects and stress in the perovskite by using one method.

[0004] As for the problem of lead leakage, in addition to improving the stability of the perovskite as much as possible and improving the service life, it has been proved that the use of active pores of crystalline porous materials to adsorb leaked lead ions is a feasible method. Inspired by crystalline porous materials, if the passivation agent molecules can be arranged and assembled into a porous structure with a certain flexibility at the perovskite grain boundaries, it is expected to passivate defects, release stress and adsorb lead ions at the same time. At present, most studies only consider adding passivation agent molecules to the perovskite material to passivate defects through active functional groups. However, there is no method for designing the perovskite grain boundaries again by using appropriate self-assembly additives to construct ordered porous structures between the grain boundaries, so as to improve the order of the grain boundaries and the perovskite active layer, and to prepare a high-stability, environment-friendly perovskite solar cell with the functions of passivating defects, releasing stress and adsorbing lead. SUMMARY

[0005] The application aims to provide a high-stability environment-friendly perovskite solar cell (PSCs), which uses a passivator with a self-assembled flexible porous structure between crystal boundaries in a photoactive layer, thereby improving the performance and stability of the PSCs in multiple aspects and promoting the environment-friendly and safe use of the PSCs.

[0006] To achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0007] A high-stability environment-friendly perovskite solar cell, which is composed of a conductive layer, a TiO2 layer, an improved photoactive layer, a hole transport layer, a MoO2 layer and a conductive layer from top to bottom; wherein the improved photoactive layer is composed of a perovskite material and a passivator which is orderly stacked at the crystal boundary of the perovskite material.

[0008] Further, the passivator is a three-dimensional molecular structure composed of one or more π planes grafted on the carbazole plane, and has a group capable of forming hydrogen bonds and interacting with perovskite; the passivator can be directionally stacked at the crystal boundary of the perovskite material through the hydrogen bonds and the stacking effect of the π planes between the passivator molecules, and form a stable space pore structure with quadrilateral pores.

[0009] Further, the π plane is selected from any one or more of carbazole, benzene, naphthalene and triphenylene, and is substituted at any one or more positions of the 1, 3, 6, 8 and 9 positions of carbazole; the substitution includes connecting between two planes by using benzene or an alkyl chain with a carbon number of 1-3, so that the obtained passivator has a flexible deformation framework.

[0010] Further, the group capable of forming hydrogen bonds and interacting with perovskite includes one or more of nitrogen-containing aromatic rings (2, 4-diamino triazine, amido pyridine, pyrazole and imidazole ketone, etc.), organic acids (carboxylic acid, sulfonic acid, sulfuric acid, etc.), cyano, thiocyanogen, amino, guanidine, ammonium group, aldehyde group.

[0011] Further, the size of the space pore formed by the passivator should be larger than the size of the lead ion.

[0012] Further, the molecular structure of the passivator also has one or more exposed active sites of nitrogen, oxygen and sulfur.

[0013] Further, the content of the passivator in the improved photoactive layer and the mass ratio of lead iodide used in the perovskite material are 1 / 10000 ~ 1 / 200.

[0014] Further, the improved photoactive layer is obtained in the following three ways:

[0015] Method one: a perovskite precursor solution containing formamidinium iodide, lead iodide, lead bromide and methylammonium bromide is prepared, a passivation agent is added and stirred uniformly, then the obtained solution is spin-coated on a hole transport layer, a reverse solvent is added in one step to form a film, and then annealing is performed to obtain the improved photoactive layer;

[0016] Method two: a perovskite precursor solution containing formamidinium iodide, lead iodide, lead bromide and methylammonium bromide is prepared, a passivation agent is added to a reverse solvent, spin-coated in one step, and then annealed to obtain the improved photoactive layer;

[0017] Method three: a passivation agent is prepared into a solution, crystals are obtained by recrystallization, and then the obtained crystals are dispersed into a lead iodide solution or a reverse solvent by ultrasonic stirring, and then the perovskite precursor solution containing formamidinium iodide, lead iodide, lead bromide and methylammonium bromide is coated according to the above-mentioned method one or method two to obtain the improved photoactive layer.

[0018] Further, the solvent used for preparing the perovskite precursor solution is one or more of N,N-dimethylformamide, dimethyl sulfoxide, etc.

[0019] Further, the reverse solvent is one or more of chlorobenzene, ethyl acetate or diethyl ether.

[0020] Further, in order to obtain better results, the passivation agent needs to be heated and stirred at 40-90 DEG C for 6-20 hours after being added; and the annealing temperature is 100-130 DEG C.

[0021] The passivation agent with a carbazole structure reported in the prior art often utilizes the functional groups in the passivation agent molecules to interact with perovskite to produce effects, without considering the interaction between the passivation agent molecules, and without considering the influence of the packing structure of the passivation agent molecules on the performance of PSCs. In addition to the functional sites of the passivation agent, the present application focuses on designing the packing structure of the passivation agent, using the pore structure formed by packing to improve the defect passivation of the grain boundary, the order degree of the grain boundary, reduce lead leakage, and eliminate film stress, so as to obtain a perovskite solar cell with high performance, high stability and low lead leakage rate.

[0022] The present application has the following advantages:

[0023] The passivation agent designed in the present application can improve the order degree of the grain boundary, passivate perovskite defects, eliminate perovskite film stress, improve the photoelectric efficiency of the perovskite battery, and also can adsorb lead ions, so as to obtain a perovskite solar cell with high performance, high stability and low lead leakage rate. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1Structure formula (a), XRD pattern (b) and packing pore structure (c) of the passivation agent 3,3',6,6'-tetracyano-9,9'-biscarbazole prepared in Example 1.

[0025] Figure 2 Surface SEM pattern of the photoactive layer prepared in Example 1.

[0026] Figure 3 Thin film stress test pattern of the photoactive layer prepared in Example 1.

[0027] Figure 4 Performance test pattern of the perovskite solar cell prepared in Example 1.

[0028] Figure 5 Stability test pattern of the perovskite solar cell prepared in Example 1.

[0029] Figure 6 NMR spectrum (a) and packing pore structure pattern (b) of the passivation agent used in Example 2. DETAILED DESCRIPTION

[0030] In order to make the content of the present application more convenient to understand, the technical solutions of the present application will be further described in combination with specific embodiments, but the present application is not limited to this.

[0031] Example 1

[0032] (1) Preparation of the passivation agent:

[0033] 3,3',6,6'-tetracyano-9,9'-biscarbazole is used as the passivation agent, and the preparation thereof comprises the following steps:

[0034] Potassium permanganate (2.371 g, 15 mmol) was added to 25 mL of acetone solution containing 3,6-dibromocarbazole (1.625 g, 5 mmol) at 50 °C. The mixture was then stirred and refluxed at 60 °C for 5 hours. After cooling to room temperature and removing the organic solvent from the solution, CHCl3 (250 mL) was added and stirred for 12 hours to extract the product. The product was washed three times with CHCl3 and recrystallized from chloroform to obtain white crystals of 3,3',6,6'-tetrabromo-9,9'-bicarbazole. CuCN (2.782 g, 31.06 mmol) and 3,3',6,6'-tetrabromo-9,9'-bicarbazole (2 g, 3.086 mmol) were then added to anhydrous N,N-dimethylformamide (50 mL). The mixture was stirred at 150 °C for 48 hours under a N2 atmosphere in a 120 mL Schleck flask. After cooling to room temperature, concentrated hydrochloric acid (40 mL) and ferric chloride (30 g, 184.9 mmol) were added, and the mixture was stirred at 0 °C for 2 hours. The product was washed with water (200 mL), filtered, and a gray solid (1.3 g, 97% yield) was collected, which was identified as 3,3',6,6'-tetracyano-9,9'-bicarbazole. ¹H NMR (400 MHz, DMSO-d6): δ 9.10 (s, 4 H), 7.91 (d, 4 H, J = 8.5 Hz), 7.32 (d, 4 H, J = 8.7 Hz); ¹³C NMR (400 MHz, DMSO-d6): δ = 141.45, 131.69, 127.12, 121.38, 119.22, 110.51, 105.12.

[0035] Depend on Figure 1 It is evident that the obtained product is free of impurities, exhibits strong ordered packing ability and good crystallinity, which is consistent with the XRD results of pore structure simulation, indicating that the self-packed product possesses a pore structure.

[0036] (2) Preparation of the photoactive layer:

[0037] A solution was prepared by adding 1.1 mmol of formamidinium iodide, 1.2 mmol of PbI₂, 0.2 mmol of methylammonium bromide, and 0.2 mmol of PbBr₂ to N,N-dimethylformamide / dimethyl sulfoxide (4:1, v / v) and stirring for 6 h. Then, 50 mL of a dimethyl sulfoxide solution containing 1.5 mol / L cesium iodide was added, and the mixture was stirred for 6 h to obtain a perovskite precursor solution. Next, 3,3',6,6'-tetracyano-9,9'-bicarbazole was added at a mass ratio of 1 / 1000 to lead iodide, and the mixture was stirred for 12 h to obtain a solution containing passivating agent molecules. 60 μL of this solution was then spin-coated onto a 10 × 10 mm substrate using a one-step method with chlorobenzene as the antisolvent. The film was then annealed at 110 °C, and after cooling, a photoactive layer was obtained.

[0038] The morphology of the obtained photoactive layer was characterized, and the results are shown in Figure 2 . As can be seen from Figure 2 , the polymer electrolyte separator without adding a passivation agent presents a porous structure, while after adding a passivation agent, the surface of the obtained film is smooth and compact, the pinholes are reduced, and the crystal grains are increased. As can be seen from Figure 3 , compared with the control group, the tensile stress value of the film prepared by adding a passivation agent decreases.

[0039] (3) Preparation of n-i-p type perovskite solar cells of FTO / TiO2 / modified perovskite layer / Spiro-OMeTAD / Ag:

[0040] FTO (1.5 x 1.5 cm 2 ) was ultrasonically cleaned with deionized water plus dishwashing liquid, acetone and ethanol for 20 minutes, respectively, and then heated at 500°C for 30 minutes. Then, 112 µL of titanium tetraisopropoxide was added to 2.5 mL of n-butanol solution, and after stirring for 1 minute, a dense titanium dioxide (bl-TiO2) solution was prepared, 70 µL of which was dropped onto the treated FTO and spin-coated at a speed of 2800 rpm for 20 s, and then heat annealed at 500°C in air for 30 minutes to deposit a dense titanium dioxide (bl-TiO2) film. After stirring the isopropanol and TiO2 slurry at room temperature for 2 days at a mass ratio of 1:20, 70 µL was dropped onto the bl-TiO2 / FTO, spin-coated at a speed of 5000 rpm for 25 s, and then heat annealed at 500°C in air for 30 minutes to deposit a mesoporous titanium dioxide (mp-TiO2) film. The photoactive layer was prepared on the obtained mp-TiO2 / bl-TiO2 / FTO substrate according to the method of step (2). Then, 40 μL of hole transport material (72.9 mg of SpiroOMeTAD) dissolved in 1 mL of chlorobenzene, 17.5 μL of Li-TFSI solution (520 mg in 1 mL of acetonitrile) and 29 μL of t-BP were added, and stirred at room temperature in the dark for 24 h, and spin-coated at 4000 rpm for 30 s. Finally, 4 nm of MoO3 and 100 nm of Ag were sequentially thermally evaporated as back electrode material by a high vacuum evaporation machine.

[0041] The J-V curve of the obtained perovskite solar cell was tested, and the results are shown in Figure 4 , 5 . As can be seen from the figure, the performance of the obtained perovskite solar cell is improved from 21.0% of the blank group to 23.2%, and the stability is also greatly improved, and after 1200 hours, the performance is still ~93% of the initial. In addition, after the battery is damaged, the leakage rate of lead is reduced by 60%.

[0042] Example 2

[0043] (1) Preparation of the passivation agent:

[0044] Using 4,4',4",4"'-(9H-carbazole-1,3,6,8-tetrayl) tetrakisbenzaldehyde as the passivation agent, its preparation includes the following steps:

[0045] Carbazole (10.0 g, 59.88 mmol) and N,N-dimethylformamide (30 ml) were mixed in a three-necked flask and stirred in an ice bath under nitrogen for 1 h to prepare solution A; N-bromosuccinimide (NBS; 43.63 g, 239.54 mmol) and N,N-dimethylformamide (200 mL) were mixed and stirred to prepare solution B; then solution B was added dropwise into solution A, stirred at room temperature for 10 h, followed by adding deionized water (200 mL) into the mixed solution to form a precipitate, which was collected after filtration, washing and drying to obtain the product intermediate 1,3,6,8-tetrabromo-9H-carbazole. The obtained intermediate 1,3,6,8-tetrabromo-9H-carbazole (1.45 g, 3 mmol), 4-formylphenylboronic acid (3.60 g, 24 mmol), potassium carbonate (3.32 g, 24 mmol) and palladium tetrakis(triphenylphosphine) (0.23 g, 0.2 mmol) were weighed into a 250 mL round-bottom flask, stirred and condensed, then the flask was vacuumed and backfilled with nitrogen three times. After mixing dioxane (40 mL) and deionized water (7 mL) and adding them into the flask, the reaction mixture was heated and refluxed for 72 h after three freeze-thaw cycles. After cooling to room temperature, dioxane and water were removed by distillation under reduced pressure to form a black solid. Then the yellow product was obtained by washing with a large amount of dichloromethane and water, which was 4,4',4",4"'-(9H-carbazole-1,3,6,8-tetrayl) tetrakisbenzaldehyde.

[0046] XRD detection showed that the obtained product had no impurities, strong ordered packing ability and good crystallinity, which was consistent with the xrd results of the pore structure simulation, indicating that the self-stacking had a pore structure (such as Figure 6 ).

[0047] (2) Preparation of the photoactive layer:

[0048] A perovskite precursor solution was prepared by stirring 1.1 mmol formamidinium iodide, 1.2 mmol PbI2, 0.2 mmol methylammonium bromide and 0.2 mmol PbBr2 in N,N-dimethylformamide / dimethyl sulfoxide (4:1, v / v) for 6 h, and then adding 50 mL of a dimethyl sulfoxide solution containing cesium iodide 1.5 mol / L and stirring for 6 h. 4,4',4",4"'-(9H-carbazole-1,3,6,8-tetrayl) tetrakisbenzaldehyde was added to chlorobenzene to prepare a dispersion solution with a concentration of 0.5 mg / L. The perovskite precursor solution was spin-coated on a 10x10 mm substrate using the obtained dispersion solution as an anti-solvent, and 150 μL of the anti-solvent was added dropwise 5 s before the end of the spin-coating. The substrate was then annealed at 110 ℃, and a photoactive layer was obtained after cooling.

[0049] (3) Preparation of a perovskite solar cell: same as step (3) of Example 1.

[0050] The prepared perovskite solar cell was tested for performance. The results showed that the performance of the obtained perovskite solar cell was improved from 19.0% of the blank group to 21.5%, and the stability was also greatly improved, with the performance still being ~90% of the initial performance after 1000 h.

[0051] Example 3

[0052] (1) Preparation of a passivation agent: same as step (1) of Example 2.

[0053] (2) Preparation of a photoactive layer: the mass ratio of the passivation agent to lead iodide was 1 / 10000, and the remaining steps were the same as step (2) of Example 1.

[0054] (3) Preparation of a perovskite solar cell: same as step (3) of Example 1.

[0055] The prepared perovskite solar cell was tested for performance. The results showed that the performance of the obtained perovskite solar cell was improved from 19.0% of the blank group to 20.9%, and the stability was also greatly improved, with the performance still being ~90% of the initial performance after 1000 h.

[0056] Example 4

[0057] (1) Preparation of a passivation agent: same as step (1) of Example 1.

[0058] (2) Preparation of photoactive layer: 0.1 g of the prepared passivation agent molecule was dissolved in N,N-dimethylformamide, heated to 130 degrees Celsius, then cooled to room temperature, ultrasonic for 1 hour, and then placed for 2 hours. The colorless crystals were collected after drying. The above crystals were dispersed into perovskite precursor solution, ultrasonic for 2 hours, stirring for 2 hours, repeating 3 times, and then filtering to obtain a precursor solution uniformly dispersed with passivation agent crystals. The content of the passivation agent was 1 / 10000 of the mass ratio of lead iodide. Then, spin coating was performed, and the method was the same as that in Example 1.

[0059] (3) Preparation of perovskite solar cell: the same as step (3) in Example 1.

[0060] The performance of the prepared perovskite solar cell was tested. The results showed that the performance of the obtained perovskite solar cell was improved from 19.0% of the blank group to 21.3%, and the stability was also greatly improved. After 1000 hours, the performance was still ~ 89% of the initial.

[0061] Example 5

[0062] (1) Preparation of passivation agent:

[0063] 3,3',6,6'-Tetracarboxylic acid-9,9'-biscarbazole was used as a passivation agent. First, 3,3',6,6'-tetracyano-9,9'-biscarbazole was prepared according to step (1) in Example 1. Then, 1 g of 3,3',6,6'-tetracyano-9,9'-biscarbazole was dissolved in 60 mL of anhydrous ethanol containing 50 mg of sodium hydroxide, and refluxed at 75°C overnight. Hydrochloric acid was added to produce a precipitate until the pH value of the system was 1. Then, the precipitate was collected by filtration and dried to obtain 3,3',6,6'-tetracarboxylic acid-9,9'-biscarbazole.

[0064] (2) Preparation of photoactive layer: the same as step (2) in Example 2.

[0065] (3) Preparation of perovskite solar cell: the same as step (3) in Example 1.

[0066] The performance of the prepared perovskite solar cell was tested. The results showed that the performance of the obtained perovskite solar cell was improved from 19.0% of the blank group to 21.38%, and the stability was also greatly improved. After 1000 hours, the performance was still ~ 88% of the initial.

[0067] Example 6

[0068] (1) Preparation of passivation agent:

[0069] 1,3-(3,3',6,6'-tetracyano-biscarbazole)-9-yl benzene was used as a passivation agent, and its preparation included the following steps: ​

[0070] Dissolve 1 g of 1,3-biscarbazol-9-ylbenzene in 6 mL of pyridine, then stir at 60 °C for 3 h, pour into 30 mL of 6 mol / L hydrochloric acid after cooling, and recrystallize in glacial acetic acid to obtain 1,3-(3,3',6,6'-tetrabromo-dicarbazol)-9-ylbenzene. Add CuCN (2.892 g) and the obtained 1,3-(3,3',6,6'-tetrabromo-dicarbazol)-9-ylbenzene (2 g) into anhydrous N,N-dimethylformamide (50 mL) in a 120 mL Schleck flask, stir at 150 °C for 48 h under N2 atmosphere, and then add concentrated hydrochloric acid (40 mL) and ferric trichloride (30 g) after cooling to room temperature. Stir at 0 °C for 2 h. Wash the product with water (200 mL), filter, and collect the gray solid, which is identified as 1,3-(3,3',6,6'-tetracyano-dicarbazol)-9-ylbenzene (2 g) (yield: 70%). ).

[0071] (2) Preparation of a photoactive layer: same as step (2) of Example 1.

[0072] (3) Preparation of a perovskite solar cell: same as step (3) of Example 1.

[0073] The prepared perovskite solar cell was tested for performance. The results showed that the performance of the obtained perovskite solar cell was improved from 19.0% of the blank group to 20.79%, and the stability was also greatly improved, and the performance was still ~ 85% of the initial performance after 1000 h.

[0074] Example 7

[0075] (1) Preparation of a passivation agent:

[0076] 3,3',6,6'-Tetrabromo-9,9'-biscarbazole was prepared according to step (1) of Example 1, and then 3,3',6,6'-tetrabromo-9,9'-biscarbazole (1.5 g), 4-formylphenylboronic acid (3.60 g), potassium carbonate (3.32 g) and palladium tetra(triphenylphosphine) (0.23 g) were weighed into a 250 mL round-bottom flask, stirred and condensed, and then the flask was vacuumed and backfilled with nitrogen three times. After mixing dioxane (40 mL) and deionized water (7 mL) and adding them into the flask, the reaction mixture was heated and refluxed for 72 h after three freeze-thaw cycles. After cooling to room temperature, the solvent was removed by distillation under reduced pressure, and the product was obtained by washing with a large amount of dichloromethane and water, which was 3,3',6,6'-tetrabromo-9,9'-biscarbazole (1.5 g) (yield: 70%). ).

[0077] (2) Preparation of photoactive layer: same as step (2) of Example 2.

[0078] (3) Preparation of perovskite solar cell: same as step (3) of Example 1.

[0079] The prepared perovskite solar cell was tested for performance. The results showed that the performance of the obtained perovskite solar cell was improved from 19.0% of the blank group to 20.68%, and the stability was also greatly improved, and the performance was still ~85% of the initial performance after 1000 hours.

[0080] The above only describes the preferred embodiments of the present application, and any changes and modifications made within the scope of the patent application of the present application shall be included in the scope of the present application.

Claims

1. A high-stability environment-friendly perovskite solar cell, characterized in that, The conductive layer, the TiO2 layer, the improved light active layer, the hole transport layer, the MoO2 layer and the conductive layer are sequentially arranged from top to bottom. The improved light active layer is composed of a perovskite material and a passivation agent orderly distributed at the grain boundary of the perovskite material. The passivation agent is a three-dimensional molecule with one or more π planes grafted on the carbazole plane, and has a group capable of forming hydrogen bonds and interacting with the perovskite. The π plane is selected from any one or more of carbazole, benzene, naphthalene and triphenylene, and is substituted at any one or more of positions 1, 3, 6, 8 and 9 of the carbazole. The size of the space hole formed by the passivation agent is greater than the size of the lead ion. 2.The high-stability environment-friendly perovskite solar cell according to claim 1, characterized in that, The substitution includes connecting two planes by using benzene or an alkyl chain with a carbon number of 1-3. 3.The high-stability environment-friendly perovskite solar cell according to claim 1, characterized in that, The group capable of forming hydrogen bonds and interacting with the perovskite includes one or more of a nitrogen-containing aromatic ring, an organic acid, a cyano group, a thiocyanato group, an amino group, a guanidine group, an ammonium group and an aldehyde group. 4.The high-stability environment-friendly perovskite solar cell of claim 1, characterized in that, The molecular structure of the passivation agent also has one or more exposed active sites of nitrogen, oxygen and sulfur.

5. The high-stability, environmentally friendly perovskite solar cell according to claim 1, characterized in that, The mass ratio of the content of the passivation agent in the improved light active layer to the lead iodide used in the perovskite material is 1 / 10000-1 / 200.

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