A passivation method for perovskite thin films based on a two-step process and a photovoltaic device

Abstract

This invention discloses a passivation method and photovoltaic device based on a two-step perovskite thin film preparation. The steps are as follows: APbX3 perovskite single crystals are pre-prepared to a certain concentration in a polar solvent; an appropriate amount of the single-crystal polar solution is added as an additive to the IPA solution of the second step (AX) to prepare the perovskite thin film in a two-step process. Wherein, A is one or more of Cs, MA, FA, Rb, PEA, GA, and BA; X is one or more of Cl, Br, and I. This invention solves the problem of numerous defects at the shallow / surface interface in perovskite thin films prepared by existing two-step methods, leading to decreased device performance. The polar solvent enhances the penetration ability of the second-step AX solution in the PbX2 layer; the single-crystal additive forms a heterojunction with the perovskite thin film, enhancing the charge transport capability of the active layer. The synergistic passivation effect yields a high-quality perovskite thin film, thereby improving the performance of the perovskite photovoltaic device.

Description

Technical Field

[0001] This invention relates to the field of perovskite solar cells, and more specifically to a passivation method for preparing perovskite thin films based on a two-step process and a photovoltaic device. Background Technology

[0002] Perovskite solar cells are considered the most promising material for next-generation photovoltaics due to their excellent photoelectric conversion efficiency (exceeding 25.8%). Improving the quality of perovskite thin films is one of the decisive factors in enhancing the efficiency of perovskite devices, and currently, there are two main methods for preparing high-quality perovskite films: one-step methods and two-step methods.

[0003] In 2009, Kojima's team first used a one-step method to prepare MAPbI3 thin films using a precursor solution of methylamine iodide and lead iodide. Their perovskite device exhibited a photoelectric conversion efficiency of 3.8%, laying a guiding foundation for the preparation and development of perovskite thin films. Subsequently, researchers proposed a one-step method using toluene as an antisolvent to obtain more uniform perovskite films, thus developing this method. However, perovskite films prepared using conventional one-step methods often have poor crystal quality and disordered crystal orientation, hindering carrier transport to the transport layer and resulting in low device performance. Furthermore, antisolvent-assisted one-step methods mostly use toxic antisolvents such as chlorobenzene, toluene, and dichloromethane, which further hinders the commercialization of perovskites.

[0004] The team has developed a high-efficiency perovskite solar cell based on a two-step perovskite thin film fabrication process. The two-step method offers better repeatability and controllability in the crystallization process, along with advantages in superior crystal orientation and crystallinity. Therefore, it overcomes the problems of poor crystallization quality and chaotic crystallization orientation in the one-step method. However, due to the unavoidable use of solution processing in the two-step method, the existing two-step method differs from the one-step method in its crystallization mechanism. Although it possesses certain advantages in crystal orientation and crystallinity, the following problems still exist in the fabrication process:

[0005] First, the quality of the perovskite film obtained by the two-step process is dependent on the quality of the PbX2 film obtained in the first step. High-quality perovskite films require a loose and porous morphology for the PbX2. However, the PbX2 prepared in the traditional two-step process tends to form a dense layered structure. In the second step, the AX component cannot penetrate deeply through the IPA solution and cannot react fully, resulting in excess residual PbX2 and reducing the quality of the perovskite film. Second, to ensure the AX component fully penetrates into the inner layer of PbX2 and achieves a more complete phase transformation, annealing at higher temperatures is usually performed during the post-processing of the film. However, the process of cooling at higher temperatures causes lattice strain in the perovskite, leading to more defect states that become non-radiative recombination centers, thus reducing device performance. Finally, the single-component perovskite active layer prepared by the two-step process needs precise coordination with the transport layer; otherwise, band alignment will be hindered, causing carrier transport obstruction and reducing device performance.

[0006] Therefore, perovskite films prepared by existing two-step processes still have a large number of defects at the shallow / surface interface, such as: I - Pb 2+ Vacancies, I-Pb antisites, grain boundaries, and other defects can act as nonradiative recombination centers for charge carriers, hindering the transport of charge carriers to the transport layer and causing a decline in device performance. Summary of the Invention

[0007] Therefore, the purpose of this invention is to solve the problem that the perovskite thin films prepared by the existing two-step method still have a large number of defects at the shallow / surface interface, which leads to the degradation of device performance, and to obtain a passivation method and photovoltaic device based on the two-step method for preparing perovskite thin films that solves the above problems.

[0008] A passivation method for preparing perovskite thin films using a two-step process includes:

[0009] Preparation of PbX2 layer: PbX2 solution was coated on the support and annealed to obtain PbX2 layer;

[0010] Perovskite thin film passivation molding: AX, AX solvent and APbX3 single crystal solution are mixed to obtain precursor solution, the precursor solution is coated on PbX2 layer, and annealing is performed to obtain passivated perovskite thin film.

[0011] The A in the AX and APbX3 single crystals each independently includes at least one of Cs (cesium), Rb (rubidium), MA (methylamino), FA (formamidinyl), PEA (phenylethylamino), BA (n-butylamino), and GA (guanidino). The A material mentioned above can also be a two-dimensional material. The X in the PbX2, AX, and APbX3 single crystals each independently includes at least one of Cl, Br, and I. The solvent of the APbX3 single crystal solution includes a polar solvent.

[0012] The concentration of the PbX2 solution is 1.2 to 1.5 mol / mL; for example: 1.2 mol / mL, 1.3 mol / mL, 1.4 mol / mL, 1.5 mol / mL.

[0013] And / or, in the precursor solution, the concentration of AX is 60 to 100 mg / mL; for example: 60 mg / mL, 65 mg / mL, 70 mg / mL, 75 mg / mL, 80 mg / mL, 85 mg / mL, 90 mg / mL, 95 mg / mL, 100 mg / mL.

[0014] And / or, the volume percentage of the polar solvent in the APbX3 single crystal solution in the precursor solution is 0.9% to 2%; for example: 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%.

[0015] And / or, the molar ratio of APbX3 single crystal to AX in the precursor solution is (0.5~2):100; for example: 0.5:100, 1:100, 1.5:100, 2:100.

[0016] The solvent for the PbX2 solution is one or more of DMF (dimethylformamide), DMSO (dimethyl sulfoxide), and NMP (N-methylpyrrolidone);

[0017] And / or, the AX solvent is IPA (isopropanol);

[0018] And / or, the polar solvent for dissolving APbX3 single crystals is at least one of DMF (N,N-dimethylformamide), DMSO (N,N-dimethyl sulfoxide), GBL (γ-butyrolactone), NMP (N-methylpyrrolidone), 2-Me (2-mercaptoethanol), and ACN (acetonitrile).

[0019] The carrier is a substrate with a transmission layer.

[0020] The substrate is one of FTO glass, ITO glass, or ITO flexible substrate, and the flexible substrate is made of one of PET (polyethylene terephthalate), PI (polyimide), or PEN (polyethylene naphthalate).

[0021] And / or, the transport layer is an N-type electron transport layer or a P-type hole transport layer.

[0022] The N-type electron transport layer is made of SnO2, ZnO, TiO2, or C. 60 PCBM([6,6]-phenyl-C 61At least one of the following: isomethyl butyrate; the material of the P-type hole transport layer is at least one of PEDOT:PSS (poly(3,4-ethylenedioxythiophene / polystyrene sulfonate), PTAA (poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine]), CuPc (copper phthalocyanine), 2PACz ([2-(9H-carbazole-9-yl)ethyl]phosphonic acid), MeO-2PACz ([2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid), NiOx (nickel oxide), Cu2O (cuprous oxide), Spiro-OMeTAD (2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene), P3HT (polymer of 3-hexylthiophene), and CuSCN (cuprous thiocyanate).

[0023] In the PbX2 layer preparation step, the annealing temperature is 70-100℃ and the annealing time is 1-5 min;

[0024] And / or, in the perovskite thin film passivation forming step, the annealing temperature is 100-150℃ and the annealing time is 20-40 min; for example, the annealing temperature is 100℃, 110℃, 120℃, 130℃, 140℃ or 150℃.

[0025] The coating method is one of spin coating, blade coating, or cloth coating.

[0026] When the coating method is spin coating, the spin coating parameters for the PbX2 solution are 1500-2000 rpm for 30-45 s; the spin coating parameters for the precursor solution are 1500-3000 rpm for 40-45 s.

[0027] When the coating method is scraping or coating, in the PbX2 layer preparation step, the scraping or coating rate of the PbX2 solution is 10-15 mm / s, and in the perovskite thin film passivation forming step, the scraping or coating rate of the precursor solution is 4-8 mm / s.

[0028] A perovskite thin film is prepared by the passivation method described above, which is based on a two-step method for preparing perovskite thin films.

[0029] A perovskite photovoltaic device includes, from top to bottom, a substrate, a carrier transport layer, a passivated perovskite thin film, a carrier transport layer, and a metal electrode layer. The passivated perovskite thin film is prepared using the above-mentioned passivation method based on a two-step perovskite thin film preparation method.

[0030] The technical solution of this invention has the following advantages:

[0031] 1. In the two-step method for preparing passivated perovskite thin films of the present invention, the APbX3 single crystal solution is an APbX3 single crystal solution pre-dissolved in a doped polar solvent. The polar solvent can appropriately adjust the polarity of the AX solution. Micro-etching of the shallow PbX2 thin film in the first step opens mesoporous channels, allowing the AX solution to penetrate more deeply, reducing the dependence of AX penetration on the morphology of the PbX2 thin film, and enabling a more complete reaction between PbX2 and AX, thereby forming a high-quality perovskite thin film. Furthermore, the enrichment of single crystals in the shallow PbX2 layer can passivate grain boundary defects and reduce the density of non-radiative recombination sites, thus improving film quality. Simultaneously, due to the different penetration rates of the AX solution from top to bottom, a gradient concentration distribution is formed between the APbX3 single crystal and the original perovskite, which is beneficial for band bending in the active layer and transport layer, making carrier transport easier and thus improving device performance. Furthermore, the APbX3 single crystal added in this invention can form a mixed perovskite phase with PbX2 and AX, which has a lower phase transition energy barrier. Therefore, it can be prepared at a lower annealing temperature, thereby alleviating the lattice strain of the perovskite unit cell and promoting the long-term stability of the device.

[0032] 2. In the second step of the two-step perovskite thin film preparation method of this invention, the APbX3 single crystal solution is pre-dissolved in a polar solvent before being doped into the AX solution. This facilitates the dissolution of APbX3 single crystals and the accurate control of the doping ratio, thereby improving the film quality. Specifically, the AX solution uses a weakly polar IPA solvent, which is only slightly soluble in APbX3 single crystals. If APbX3 single crystals are directly added to the AX solution, they may not dissolve, forming a particulate suspension that hinders the penetration of APbX3 single crystals into the shallow surface layer of the PbX2 film and the deep penetration of AX. If APbX3 single crystals are directly doped and then a polar solvent is added, the mixing will also be uneven, and the amount of polar solvent is difficult to adjust. This method cannot achieve a mixed solvent that can dissolve APbX3 single crystals without being too polar. Insufficient polar solvent will result in the APbX3 single crystal failing to dissolve, leading to uneven mixing. Conversely, excessive polar solvent will result in an overly polar mixed solvent, causing the PbX2 in the first step to dissolve upon introduction into the second step. This invention, by mixing the polar solvent used to dissolve the APbX3 single crystal with a non-polar IPA solvent, facilitates the adjustment of the polarity of the precursor solution in the second step. This allows for better opening of the mesoporous windows of the PbX2 film from the first step, promoting deeper penetration of the precursor and a more complete reaction. Therefore, the method of this invention, which uses a polar solvent to pre-dissolve the APbX3 single crystal before doping it into a non-polar AX solution, effectively improves the film quality.

[0033] 3. In the method of the present invention, adding APbX3 single crystal solution to the AX solution in the second step is beneficial for combining with PbX2 prepared by vacuum method to passivate large-area thin films. Attached Figure Description

[0034] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. (Note the correspondence between the embodiments and comparative drawings; refer to the disclosure document to check if they correspond to this document. The correspondence in this document is incorrect.)

[0035] Figure 1 This is a schematic diagram of the fabrication process of the perovskite photovoltaic device in this invention.

[0036] Figure 2 These are scanning electron microscope (SEM) images of the passivated perovskite films prepared in Example 1 and Comparative Example 1 of this invention, wherein a is the SEM image of Example 1 and b is the SEM image of Comparative Example 1.

[0037] Figure 3 These are scanning electron microscope (SEM) images of the passivated perovskite films prepared in Example 7 and Comparative Example 7 of this invention, where a is the SEM image of Example 7 and b is the SEM image of Comparative Example 7. Detailed Implementation

[0038] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0039] Where specific experimental steps or conditions are not specified in the embodiments, they can be performed according to the conventional experimental steps or conditions described in the literature in this field.

[0040] Example 1

[0041] The fabrication process of a perovskite photovoltaic device is as follows:

[0042] Step 1: Clean the 1.5×1.5cm FTO glass in an ultrasonic cleaner with deionized water, detergent, acetone and isopropanol in sequence for 15 minutes, and then dry it in a 60℃ oven for later use.

[0043] Step 2: Dilute 15wt% (mass percentage) of commercial SnO2 sol with deionized water at a volume ratio of 1:5. After treating the prepared FTO glass in a UV ozone generator for 15 minutes, add 40uL of the diluted SnO2 sol and spin coat it at 4000rpm for 30s. Then anneal it at 150℃ for 30 minutes and let it cool naturally for later use.

[0044] Step 3: Dissolve PbI2 in a mixed solvent of DMF and DMSO at a volume ratio of 19:1 to prepare a 1.5 mol / mL PbX2 solution. Then, take 50 μL of the PbX2 solution and spin-coat it onto the film from Step 2 at 1500 rpm for 45 s. Anneal at 70 °C for 1 min and cool for later use. Pre-dissolve the purchased MAPbBr3 single crystal in DMF to prepare a 339 mg / mL APbX3 single crystal solution for later use. Dissolve 90 mg FAI, 9 mg MACl, and 20 μL of the APbX3 single crystal solution in 1 mL of IPA solvent to prepare a precursor solution. Take 50 μL of the precursor solution and spin-coat it onto PbI2 at 1700 rpm for 40 s. Anneal at 150 °C for 30 min in air with a relative humidity (RH) of 40% and cool for later use. The scanning electron microscope image of the passivated perovskite film formed in this step is shown below. Figure 2 As shown in Figure a.

[0045] Step 4: Dissolve 72.3 mg Spiro-OMeTAD in 1 mL of chlorobenzene, add 35 μL Li-TFSI (260 mg / mL acetonitrile solution) and 30 μL TBP (4-tert-butylpyridine), and mix thoroughly to obtain a mixture. Take 40 μL of this mixture and spin-coat a hole transport layer at 3000 rpm for 30 s. Finally, deposit 10 nm of Au at a rate of 0.2 Å / s in a vacuum coating apparatus, and then deposit 70 nm of Au at a rate of 1 Å / s to obtain the desired layer. Figure 1 The complete perovskite photovoltaic device shown.

[0046] Example 2

[0047] The fabrication process of a perovskite photovoltaic device is described in this embodiment. The difference between this embodiment and Embodiment 1 is that, except for step 3, the remaining operations are identical. Step 3 in this embodiment is as follows:

[0048] Step 3: Dissolve PbI2 in a mixed solvent of DMF and DMSO at a volume ratio of 19:1 to prepare a 1.5 mol / mL PbX2 solution. Then, take 50 μL of the PbX2 solution and spin-coat it onto the film prepared in Step 2 at 1500 rpm for 45 s. Anneal at 100 °C for 1 min and cool for later use. Pre-dissolve the purchased finished CsPbBr3 single crystal in DMF to prepare a 136 mg / mL APbX3 single crystal solution for later use. Dissolve 90 mg FAI, 9 mg MACl, and 20 μL of APbX3 single crystal solution in 1 mL of IPA solvent to prepare a precursor solution. Take 50 μL of the precursor solution and spin-coat it onto PbI2 at 1700 rpm for 40 s. Anneal at 150 °C for 30 min in air with a relative humidity (RH) of 40% and cool for later use.

[0049] Example 3

[0050] A fabrication process for a perovskite photovoltaic device is described in this embodiment. The difference between this embodiment and Embodiment 1 is that, apart from the different raw materials used in each step, all other parameters and conditions are identical. The raw materials used in each step of this embodiment are as follows:

[0051] In step 2: The purchased TiO2 gel with a particle size of about 5nm is mixed with deionized water and IPA to form a sol to replace the SnO2 sol. The ratio of TiO2 gel to deionized water and IPA is 13mg, 4mL and 1mL, respectively.

[0052] In step 3: PbI2 is dissolved in a mixed solvent of DMF and NMP at a volume ratio of 8:1 to prepare a 1.5 mol / mL PbX2 solution. Then, 50 μL of the PbX2 solution is spin-coated onto the film prepared in step 2 at 1500 rpm for 45 s, and annealed at 70 °C for 1 min. After cooling, it is ready for use. The purchased finished MAPbBr3 single crystal is pre-dissolved in DMSO to prepare a 508 mg / mL APbX3 single crystal solution. 90 mg FAI, 9 mg MACl, and 10 μL of APbX3 single crystal solution are dissolved in 1 mL of IPA solvent to prepare a precursor solution. 50 μL of the precursor solution is spin-coated onto PbI2 at 1700 rpm for 40 s, and annealed at 150 °C for 30 min in air with a relative humidity (RH) of 40%. After cooling, it is ready for use.

[0053] Example 4

[0054] A fabrication process for a perovskite photovoltaic device is described in this embodiment. The difference between this embodiment and Embodiment 1 is that, apart from the different raw materials used in each step, all other parameters and conditions are identical. The raw materials used in each step of this embodiment are as follows:

[0055] In step 2: The purchased TiO2 gel with a particle size of about 5nm is mixed with deionized water and IPA to form a sol to replace the SnO2 sol. The ratio of TiO2 gel to deionized water and IPA is 13mg, 4mL and 1mL, respectively.

[0056] In step 3: PbI2 is dissolved in a mixed solvent of DMF and DMSO at a volume ratio of 19:1 to prepare a 1.5 mol / mL PbX2 solution. Then, 50 μL of the PbX2 solution is spin-coated onto the film from step 2 at 1500 rpm for 45 s, and annealed at 70 °C for 1 min. After cooling, it is ready for use. The purchased finished RbPbBr3 single crystal is pre-dissolved in a mixed solution of DMF:NMP = 4:1 to prepare a 217 mg / mL APbX3 single crystal solution. 90 mg FAI, 9 mg MACl, and 20 μL of APbX3 single crystal solution are dissolved in 1 mL of IPA solvent to prepare a precursor solution. 50 μL of the precursor solution is spin-coated onto PbI2 at 1700 rpm for 40 s, and annealed at 150 °C for 30 min in air with a relative humidity (RH) of 40%. After cooling, it is ready for use.

[0057] Example 5

[0058] A fabrication process for a perovskite photovoltaic device is described in this embodiment. The difference between this embodiment and Embodiment 1 is that, apart from the different raw materials used in each step, all other parameters and conditions are identical. The raw materials used in each step of this embodiment are as follows:

[0059] In step 3: PbI2 and PbCl2 are dissolved in a 50:1 molar ratio in a mixed solvent of DMF and DMSO with a volume ratio of 19:1 to prepare a 1.5 mol / mL PbX2 solution. Then, 50 μL of the PbX2 solution is spin-coated onto the film from step 2 at 1500 rpm for 45 s, and annealed at 70 °C for 1 min. After cooling, it is ready for use. The purchased finished BAPbBr3 single crystal is pre-dissolved in DMF to prepare an 85 mg / mL APbX3 single crystal solution. 90 mg FAI, 9 mg MACl, and 20 μL of APbX3 single crystal solution are dissolved in 1 mL of IPA solvent to prepare a precursor solution. 50 μL of the precursor solution is spin-coated onto a mixture of PbI2 and PbCl2 at 1700 rpm for 40 s, and annealed at 150 °C for 30 min in air with a relative humidity (RH) of 40%. After cooling, it is ready for use.

[0060] Example 6

[0061] A fabrication process for a perovskite photovoltaic device is described in this embodiment. The difference between this embodiment and Embodiment 1 is that, apart from the different raw materials used in each step, all other parameters and conditions are identical. The raw materials used in each step of this embodiment are as follows:

[0062] In step 2: The purchased TiO2 gel with a particle size of about 5nm is mixed with deionized water and IPA to form a sol to replace the SnO2 sol. The proportions of TiO2 gel, deionized water and IPA are 13mg, 4mL and 1mL, respectively.

[0063] In step 3: PbI2 is dissolved in a mixed solvent of DMF and DMSO at a volume ratio of 19:1 to prepare a 1.5 mol / mL PbX2 solution. Then, 50 μL of the PbX2 solution is spin-coated onto the film prepared in step 2 at 1500 rpm for 45 s, and annealed at 70 °C for 1 min. After cooling, it is ready for use. The purchased finished MAPbBr3 single crystal is pre-dissolved in NMP to prepare a 285 mg / mL APbX3 single crystal solution. 80 mg MAI, 4 mg MACl, and 20 μL of APbX3 single crystal solution are dissolved in 1 mL of IPA solvent to prepare a precursor solution. 50 μL of the precursor solution is spin-coated onto PbI2 at 1700 rpm for 40 s, and annealed at 100 °C for 30 min in air with a relative humidity (RH) of 40%. After cooling, it is ready for use.

[0064] Example 7

[0065] The fabrication process of a perovskite photovoltaic device is as follows:

[0066] Step 1: Clean the 1.5×1.5cm FTO glass in an ultrasonic cleaner with deionized water, detergent, acetone and isopropanol in sequence for 15 minutes, and then dry it in a 60℃ oven for later use.

[0067] Step 2: Dissolve 4 mg of PTAA in chlorobenzene to prepare a PTAA solution with a concentration of 4 mg / mL. After treating the FTO glass in a UV ozone generator for 15 min, add 40 μL of PTAA solution, then spin coat at 4000 rpm for 30 s, anneal at 100 °C for 10 min, and let it cool naturally for later use.

[0068] Step 3: Dissolve PbI2 in a mixed solvent of DMF and DMSO at a volume ratio of 19:1 to prepare a 1.5 mol / mL PbX2 solution. Then, spin-coat 50 μL of the PbX2 solution onto the film from Step 2 at 1500 rpm for 45 s, and anneal at 70 °C for 1 min. After cooling, set aside. Pre-dissolve the purchased CsPbBr3 single crystal in DMSO to prepare a 547 mg / mL APbX3 single crystal solution. Set aside. Dissolve 90 mg FAI, 9 mg MACl, and 10 μL of the APbX3 single crystal solution in 1 mL of IPA solvent to prepare a precursor solution. Deposit 50 μL of the precursor solution onto PbI2 at 1700 rpm for 40 s using spin-coating, and anneal at 110 °C for 30 min in air with a relative humidity (RH) of 40%. After cooling, set aside. The scanning electron microscope image of the passivated perovskite film formed in this step is shown below. Figure 3 As shown in Figure a.

[0069] Step 4: Dissolve 18 mg PCBM in 1 mL of chlorobenzene to obtain a mixture. Take 40 μL of this mixture and spin-coat it at 3000 rpm for 30 s to prepare an electron transport layer. Finally, deposit 5 nm of BCP in a vacuum coating apparatus at a rate of 0.1 Å / s, and then deposit 100 nm of Ag at a rate of 1 Å / s to obtain a complete perovskite photovoltaic device.

[0070] Example 8

[0071] The fabrication process of a perovskite photovoltaic device is described in this embodiment. The difference between this embodiment and Embodiment 7 is that, apart from the different raw materials used in each step, all other parameters and conditions are exactly the same. The raw materials used in each step of this embodiment are as follows:

[0072] In step 2: 2 mg of NiOx nanocrystalline powder was used to prepare a NiOx sol with a concentration of 2 mg / mL in a solution of deionized water:IPA = 3:1. The NiOx solution was used instead of the PTAA solution in Example 7.

[0073] In step 3: PbI2 is dissolved in a mixed solvent of DMF and DMSO at a volume ratio of 19:1 to prepare a 1.5 mol / mL PbX2 solution. Then, 50 μL of the PbX2 solution is spin-coated onto the film prepared in step 2 at 1500 rpm for 45 s, and annealed at 70 °C for 1 min. After cooling, it is ready for use. The purchased finished CsPbI3 single crystal is pre-dissolved in DMF to prepare a 150 mg / mL APbX3 single crystal solution. 90 mg FAI, 9 mg MACl, and 20 μL of APbX3 single crystal solution are dissolved in 1 mL of IPA solvent to prepare a precursor solution. 50 μL of the precursor solution is spin-coated onto PbI2 at 1700 rpm for 40 s, and annealed at 130 °C for 30 min in air with a relative humidity (RH) of 40%. After cooling, it is ready for use.

[0074] In step 4: Finally, 25 nm C layers are sequentially deposited in a vacuum coating apparatus at a rate of 0.2 Å / s. 60 A complete perovskite photovoltaic device is fabricated by depositing 100nm Ag at a rate of 1 angstrom / second with 5nm BCP.

[0075] Example 9

[0076] The fabrication process of a perovskite photovoltaic device is described in this embodiment. The difference between this embodiment and Embodiment 7 is that, apart from the different raw materials used in each step, all other parameters and conditions are exactly the same. The raw materials used in each step of this embodiment are as follows:

[0077] In step 2: 2PACz is dissolved in chlorobenzene to prepare a 2PACz solution with a concentration of 2 mg / mL. The 2PACz solution is used instead of the PTAA solution in Example 7.

[0078] In step 3: PbI2 is dissolved in a mixed solvent of DMF and DMSO at a volume ratio of 19:1 to prepare a 1.5 mol / mL PbX2 solution. Then, 50 μL of the PbX2 solution is spin-coated onto the film from step 2 at 1500 rpm for 45 s, and annealed at 70 °C for 1 min. After cooling, it is ready for use. The purchased finished RbPbBr3 single crystal is pre-dissolved in a mixed solution of DMF:NMP = 4:1 to prepare a 217 mg / mL APbX3 single crystal solution. 90 mg FAI, 9 mg MACl, and 20 μL of APbX3 single crystal solution are dissolved in 1 mL of IPA solvent to prepare a precursor solution. 50 μL of the precursor solution is spin-coated onto PbI2 at 1700 rpm for 40 s, and annealed at 120 °C for 30 min in air with a relative humidity (RH) of 40%. After cooling, it is ready for use.

[0079] Example 10

[0080] The fabrication process of a perovskite photovoltaic device is described in this embodiment. The difference between this embodiment and Embodiment 7 is that, apart from the different raw materials used in each step, all other parameters and conditions are exactly the same. The raw materials used in each step of this embodiment are as follows:

[0081] In step 2: 2 mg of NiOx nanocrystal powder was prepared into a NiOx sol with a concentration of 2 mg / mL in a solution of deionized water:IPA = 3:1. The NiOx sol was used to replace the PTAA solution in Example 7.

[0082] In step 3: PbI2 is dissolved in a mixed solvent of DMF and DMSO at a volume ratio of 19:1 to prepare a 1.5 mol / mL PbX2 solution. Then, 50 μL of the PbX2 solution is spin-coated onto the film prepared in step 2 at 1500 rpm for 45 s, and annealed at 70 °C for 1 min. After cooling, it is ready for use. The purchased finished MAPbBr3 single crystal is pre-dissolved in NMP to prepare a 339 mg / mL APbX3 single crystal solution. 90 mg FAI, 9 mg MACl, and 10 μL of APbX3 single crystal solution are dissolved in 1 mL of IPA solvent to prepare a precursor solution. 50 μL of the precursor solution is spin-coated onto PbI2 at 1700 rpm for 40 s, and annealed at 150 °C for 30 min in air with a relative humidity (RH) of 40%. After cooling, it is ready for use.

[0083] In step 4: Finally, 25 nm C layers are sequentially deposited in a vacuum coating apparatus at a rate of 0.2 Å / s. 60 A complete perovskite photovoltaic device is fabricated by depositing 100nm Ag at a rate of 1 angstrom / second with 5nm BCP.

[0084] Example 11

[0085] The difference between this embodiment and Embodiment 1 is that, in step (3), after the precursor solution is spin-coated onto PbI2, the annealing conditions are changed from annealing at 150°C for 30 min in air with a relative humidity (RH) of 40% to annealing at 130°C for 20 min in air with a relative humidity (RH) of 40%.

[0086] Comparative Example 1

[0087] The fabrication process of a perovskite photovoltaic device is described in this comparative example. The difference between this example and Example 1 is that step 3 is different, while the other parameters and conditions are exactly the same.

[0088] Step 3: Dissolve PbI2 in a mixed solvent of DMF and DMSO at a volume ratio of 19:1 to prepare a 1.5 mol / mL PbX2 solution. Then, spin-coat 50 μL of the PbX2 solution onto the film from Step 2 at 1500 rpm for 45 s, anneal at 70 °C for 1 min, and cool for later use. Dissolve 90 mg FAI, 6 mg MABr, and 9 mg MACl in 1 mL of IPA to prepare a precursor solution. Spin-coat 50 μL of the precursor solution onto PbI2 at 1700 rpm for 40 s, anneal at 150 °C for 30 min in air with a relative humidity (RH) of 40%, and cool for later use. The scanning electron microscope image of the perovskite film formed in this step is shown below. Figure 2 As shown in b.

[0089] Comparative Example 2

[0090] The difference between this comparative example and Example 2 is that no single crystal solution is added in step 3, and CsBr, which is homologous to the A and X sites of the single crystal, is used instead. The preparation steps of the precursor solution are as follows: FAI, MACl, and CsBr are added to 1 mL of IPA solution in amounts of 90 mg, 9 mg, and 3 mg respectively. The other steps are the same as in Example 2.

[0091] Comparative Example 3

[0092] The difference between this comparative example and Example 3 is that no single crystal solution is added in step 3, and MABr, which is homologous to the A and X sites of the single crystal, is used instead. The preparation steps of the precursor solution are as follows: FAI, MACl, and MABr are added to 1 mL of IPA solution in amounts of 90 mg, 9 mg, and 6 mg respectively. The other steps are the same as in Example 3.

[0093] Comparative Example 4

[0094] The difference between this comparative example and Example 4 is that no single crystal solution is added in step 3, and a substance with the same A and X sites as the single crystal solution is used to replace the single crystal solution. Otherwise, it is completely the same as Example 4. Specifically, in this comparative example, RbBr with the same A and X sites as the single crystal is used, that is, 2 mg of RbBr replaces the 20 μL of RbPbBr3 single crystal solution in Example 4. Otherwise, it is the same as Example 4.

[0095] Comparative Example 5

[0096] The difference between this comparative example and Example 5 is that no single crystal solution is added in step 3, and a substance with the same A and X sites as the single crystal solution is used to replace the single crystal solution. Otherwise, it is exactly the same as Example 5. Specifically, 1.5 mg of PEAI is used to replace 20 μL of PEAPbI3 single crystal solution in Example 5, and everything else is the same as in Example 5.

[0097] Comparative Example 6

[0098] The difference between this comparative example and Example 6 is that no single crystal solution is added in step 3, and a substance with the same A and X sites as the single crystal solution is used to replace the single crystal solution. Otherwise, it is completely the same as Example 6. Specifically, 4 mg of MABr is used to replace the 20 μL MAPbBr3 single crystal solution in Example 6, and everything else is the same as Example 6.

[0099] Comparative Example 7

[0100] The fabrication process of a perovskite photovoltaic device is as follows:

[0101] Step 1: Clean the 1.5×1.5cm FTO glass in an ultrasonic cleaner with deionized water, detergent, acetone and isopropanol in sequence for 15 minutes, and then dry it in a 60℃ oven for later use.

[0102] Step 2: Dissolve 4 mg of PTAA in chlorobenzene to prepare a PTAA solution with a concentration of 4 mg / mL. After treating the FTO glass in a UV ozone generator for 15 min, add 40 μL of PTAA solution and spin coat it at 4000 rpm for 30 s. Then anneal it at 100 °C for 10 min and let it cool naturally for later use.

[0103] Step 3: Dissolve PbI2 in a mixed solvent of DMF and DMSO at a volume ratio of 19:1 to prepare a 1.5 mol / mL PbX2 solution. Then, take 50 μL of the PbX2 solution and spin-coat it onto the film from Step 2 at 1500 rpm for 45 s. Anneal at 70 °C for 1 min and cool for later use. Dissolve 90 mg FAI, 6 mg CsBr, and 9 mg MACl in 1 mL of IPA to prepare a precursor solution. Take 50 μL of the precursor solution and spin-coat it onto PbI2 at 1700 rpm for 40 s. Anneal at 110 °C for 20 min in air with a relative humidity (RH) of 40% and cool for later use. The scanning electron microscope image of the perovskite film formed in this step is shown below. Figure 3 As shown in b.

[0104] Step 4: Dissolve 18 mg PCBM in 1 mL of chlorobenzene to obtain a mixture. Take 40 μL of this mixture and spin-coat it at 3000 rpm for 30 s to prepare an electron transport layer. Finally, deposit 5 nm of BCP in a vacuum coating apparatus at a rate of 0.1 Å / s, and then deposit 100 nm of Ag at a rate of 1 Å / s to obtain a complete perovskite photovoltaic device.

[0105] Comparative Example 8

[0106] The difference between this comparative example and Example 8 is that no single crystal solution is added in step 3, and a substance with the same A and X sites as the single crystal solution is used to replace the single crystal solution. Otherwise, it is completely the same as Example 8. Specifically, in this comparative example, 3 mg of CsI is used to replace the 20 μL of CsPbI3 single crystal solution in Example 8; otherwise, it is the same as Example 8.

[0107] Comparative Example 9

[0108] The difference between this comparative example and Example 9 is that no single crystal solution is added in step 3, and a substance with the same A and X sites as the single crystal solution is used to replace the single crystal solution. Otherwise, it is completely the same as Example 9. Specifically, in this comparative example, 2 mg of RbBr is used instead of the 20 μL RbPbBr3 single crystal solution in Example 9; otherwise, it is the same as Example 9.

[0109] Comparative Example 10

[0110] The difference between this comparative example and Example 10 is that no single crystal solution is added in step 3, and a substance with the same A and X sites as the single crystal solution is used to replace the single crystal solution. Otherwise, it is exactly the same as Example 10. Specifically, 6 mg of MABr is used to replace 20 μL of MAPbBr3 single crystal solution in Example 10, and everything else is the same as in Example 10.

[0111] Comparative Example 11

[0112] The difference between this comparative example and Comparative Example 1 is that, in step (3), after the precursor solution is spin-coated onto PbI2, the annealing conditions are changed from annealing at 150°C for 30 min in air with a relative humidity (RH) of 40% to annealing at 130°C for 20 min in air with a relative humidity (RH) of 40%.

[0113] Experimental example:

[0114] The perovskite photovoltaic devices prepared using the examples and comparative examples were subjected to current-voltage tests under AM1.5G standard sunlight to obtain their short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), and photoelectric conversion efficiency (PCE). The results are shown in Table 1.

[0115] Table 1

[0116]

[0117] By comparing the results of Examples 1-10 and the corresponding Comparative Examples 1-10 in Table 1 above, it can be seen that in the two-step perovskite thin film preparation process, adding APbX3 single crystal solution in the second step can effectively improve the film quality and thus effectively enhance the photoelectric conversion efficiency of the device.

[0118] Comparing Comparative Example 11 with Comparative Example 1, it can be seen that lowering the annealing temperature significantly reduces the photoelectric conversion efficiency of the device when no single crystal is added. Furthermore, comparing the results of Example 1 with Example 11, it can be seen that APbX3 single crystal forms a mixed perovskite phase with PbX2 and AX, which has a lower phase transition energy barrier. Therefore, perovskite thin films can be prepared under conditions of lower annealing temperature, and the performance of low-temperature annealing is similar to that of high-temperature annealing. Low-temperature annealing helps to alleviate the lattice strain of perovskite unit cells, reduce defects, and is beneficial to the long-term stability of the device.

[0119] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A passivation method for the preparation of perovskite thin films based on a two-step method, characterized by, include: Preparation of PbX2 layer: PbX2 solution was coated on the support and annealed to obtain PbX2 layer; Perovskite thin film passivation molding: A precursor solution is obtained by mixing AX, AX solvent and APbX3 single crystal solution, the precursor solution is coated on PbX2 layer, and annealed to obtain a passivated perovskite thin film; the AX solvent is isopropanol. The A in the AX and APbX3 single crystals each independently includes any one or more of cesium, rubidium, methylamino, formamidinyl, phenylethylamino, n-butylamino, and guanidine; the X in the PbX2, AX, and APbX3 single crystals each independently includes any one or more of Cl, Br, and I; the solvent of the APbX3 single crystal solution includes a polar solvent; the polar solvent is at least one of N,N-dimethylformamide, N,N-dimethyl sulfoxide, γ-butyrolactone, N-methylpyrrolidone, 2-mercaptoethanol, and acetonitrile.

2. The method of claim 1, wherein, The concentration of the PbX2 solution is 1.2–1.5 mol / mL; And / or, the concentration of AX in the precursor solution is 60–100 mg / mL; And / or, the volume percentage of the polar solvent in the APbX3 single crystal solution in the precursor solution is 0.9%–2%; And / or, the molar ratio of APbX3 single crystal to AX in the precursor solution is (0.5~2):

100.

3. The method according to claim 1 or 2, characterized in that, The solvent for the PbX2 solution is one or more of dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

4. The method according to claim 1 or 2, characterized in that, In the PbX2 layer preparation step, the annealing temperature is 70-100℃ and the annealing time is 1-5 min.

5. The method according to claim 1 or 2, characterized in that, In the perovskite thin film passivation forming step, the annealing temperature is 100-150℃ and the annealing time is 20-40 min.

6. The method according to claim 1 or 2, characterized in that, The coating method is one of spin coating, blade coating, or cloth coating.

7. The method according to claim 6, characterized in that, When the coating method is spin coating, the spin coating parameters for the PbX2 solution are 1500-2000 rpm for 30-45 s; the spin coating parameters for the precursor solution are 1500-3000 rpm for 40-45 s.

8. The method according to claim 6, characterized in that, When the coating method is scraping or coating, the scraping or coating rate of the PbX2 solution is 10-15 mm / s, and the scraping or coating rate of the precursor solution is 4-8 mm / s.

9. A perovskite thin film, characterized in that, The perovskite thin film was prepared using a two-step method as described in any one of claims 1-8.

10. A perovskite photovoltaic device, characterized in that, The material comprises a substrate, a carrier transport layer, a perovskite thin film, a carrier transport layer, and a metal electrode layer arranged sequentially, wherein the perovskite thin film is prepared by the passivation method described in any one of claims 1-8.

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