Perovskite precursor solution, perovskite thin film, perovskite battery and preparation method thereof

Abstract

The invention provides a perovskite precursor solution, a perovskite thin film, a perovskite battery and a preparation method thereof. The perovskite precursor solution comprises the following components: a perovskite material, a self-assembly monomolecular layer forming agent, an ionic liquid and a solvent. According to the invention, the specific SAM material and the ionic liquid are doped into the perovskite precursor solution at the same time to construct a dual protection system: on one hand, a compact monomolecular layer formed by SAM on the surface and interface of the perovskite film can effectively block the permeation of water molecules and oxygen, and reduce the hydrolysis and oxidation of the perovskite material; and on the other hand, the ionic liquid can form a supporting structure in the perovskite thin film, thin film cracking and ion migration caused by temperature change are inhibited, and meanwhile, the SAM layer is protected from being eroded and damaged by a perovskite solvent. Through the synergistic effect of the two, the service life of the perovskite solar cell under the actual working condition is greatly prolonged, and the requirement of commercial application for stability is met.

Description

Technical Field

[0001] This invention belongs to the field of perovskite battery technology, specifically relating to a perovskite precursor solution, a perovskite thin film, a perovskite battery, and a method for preparing the same. Background Technology

[0002] In the context of dual carbon emissions, green, pollution-free, and clean renewable energy plays a crucial role in the global energy transition. Perovskite solar cells (PSCs), as an emerging technology, are expected to further reduce power generation costs and accelerate the global energy transition due to their advantages such as high photoelectric conversion efficiency, low manufacturing cost, good performance in low light conditions, and compatibility with other types of cells. Furthermore, the flexible and rigid substrates of perovskite cells allow for more diverse applications compared to first- and second-generation solar cells.

[0003] However, perovskite solar cells still face many challenges in practical applications. Most high-efficiency organic-inorganic halide perovskite solar cells use polycrystalline perovskite thin films as their light-absorbing layers, which contain numerous defects, including uncoordinated iodide ions, uncoordinated lead ions, and lead clusters. These defects lead to severe charge recombination and ion migration at the interface, with the defect state density approximately 100 times higher than that of the bulk light-absorbing layer, significantly impacting the device's energy conversion efficiency and stability.

[0004] Adding additives to the perovskite layer is a common method to improve the photoelectric conversion efficiency and stability of perovskite solar cells. A wide variety of additives are available, including small organic molecules, polymers, organic-inorganic salts, and nanoparticles. Among these, ionic liquids, as salts composed of anions and cations and liquid at room temperature, exhibit significant advantages in the field of perovskite solar cells due to their unique physicochemical properties. Ionic liquids possess characteristics such as low toxicity, low saturated vapor pressure, high ionic conductivity, and excellent chemical stability. They can interact with defect sites in perovskite, repairing or neutralizing defects, and passivating them, thereby improving the photoelectric performance of perovskite, increasing charge transport efficiency, reducing non-radiative recombination losses, and enhancing the photoelectric conversion efficiency of the cell. For example, imidazole cations in some ionic liquids have excellent charge transport performance and stability, effectively improving the photoelectric performance of perovskite. However, traditional ionic liquid-based additives, such as 1-butyl-3-methylimidazolium tetrafluoroborate ((BMIM)BF4) and 1-butyl-3-methylimidazolium hexafluorophosphate ((BMIM)PF6), have several shortcomings. These additives make it difficult to achieve high stability in perovskite solar cells. When exposed to external stimuli such as moisture, oxygen, high temperature, and ultraviolet radiation, they can easily affect ion migration, leading to a decline in solar cell performance. In summary, the use of ionic liquids as additives in existing perovskite solar cell technology has certain limitations. Summary of the Invention

[0005] To overcome the problems existing in the prior art, one objective of this invention is to provide a perovskite precursor solution. A second objective is to provide a perovskite thin film. A third objective is to provide a method for preparing the aforementioned perovskite thin film. A fourth objective is to provide a perovskite solar cell.

[0006] This invention innovatively incorporates specific SAM materials and ionic liquids into a perovskite precursor solution, forming a high-quality perovskite thin film through solution processing. Combined with an optimized battery structure design, this achieves performance enhancement.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a perovskite precursor solution comprising the following components: perovskite material, a self-assembled monolayer forming agent, an ionic liquid, and a solvent.

[0008] Self-assembled monolayers (SAMs) have wide applications in the field of material surface modification. This invention reveals that introducing SAMs into the bottom interface of perovskite solar cells can improve cell performance to some extent. However, the bottom SAMs are easily washed away by the perovskite solvent on top, resulting in an uneven interface, which in turn affects non-radiative recombination and limits further improvements in cell efficiency and stability.

[0009] This invention simultaneously dops specific SAM materials and ionic liquids into a perovskite precursor solution, constructing a dual-protection system: On one hand, the dense monolayer formed by SAM on the surface and interface of the perovskite film effectively blocks the penetration of water molecules and oxygen, reducing hydrolysis and oxidation of the perovskite material; on the other hand, the low saturated vapor pressure, high chemical stability, and thermal stability of the ionic liquid can form a supporting structure inside the perovskite film, inhibiting film cracking and ion migration caused by temperature changes, while protecting the SAM layer from erosion and damage by the perovskite solvent. Through the synergistic effect of these two components, the lifespan of perovskite solar cells under actual operating conditions is significantly extended, meeting the stability requirements for commercial applications.

[0010] Preferably, the self-assembled monolayer forming agent includes at least one of phosphonic acid self-assembled monolayer forming agents and thiol-based self-assembled monolayer forming agents.

[0011] More preferably, the phosphonic acid self-assembly monolayer forming agent includes at least one of (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid (Me-4PACz), polycarbazole phosphonic acid (Poly-4PACz), (2-(9H-carbazole-9-yl)ethyl)phosphonic acid (2PACz), (2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl)phosphonic acid (MeO-4PACz), and [2-(9,10-dihydro-9,9-dimethylacridin-10-yl)ethyl]phosphonic acid (2PADmA).

[0012] More preferably, the thiol-based self-assembled monolayer forming agent includes at least one of 2-mercaptopropionic acid and 3-mercaptopropionic acid.

[0013] Preferably, the ionic liquid includes at least one of imidazole ionic liquids, pyridine ionic liquids, quaternary ammonium ionic liquids, pyrrolidine ionic liquids, piperidine ionic liquids, functionalized ionic liquids, and guanidine salt ionic liquids.

[0014] More preferably, the imidazole ionic liquid includes at least one of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (HMTTSI), 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMIMTFSI), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), and 1-(2-methoxyethyl)-1-methylpyrrolidine bis(trifluoromethanesulfonyl)amide (MMPyTFSI).

[0015] More preferably, the guanidine salt ionic liquid comprises tetramethylguanidine tetrafluoroborate (TMGBF4).

[0016] Preferably, the perovskite material is selected from ABX3; wherein A is at least one of MA, MDA, FA, PEA, Cs, Rb and K; MA is CH3NH3; MDA is NH3CH2NH3; FA is NH2CHNH2; PEA is C8H9NH3; B is at least one of Pb, Sn and Ge; and X is at least one of F, Cl, Br and I.

[0017] More preferably, the perovskite material is prepared from a perovskite precursor material, which includes an A-site raw material and a B-site raw material. The A-site raw material includes at least one of CsI, CsBr, CsCl, MABr, MAI, MACl, FAI, FABr, FACl, (FA,MA)I, and (FA,MA)Br. The B-site raw material includes at least one of PbBr2, PbI2, PbCl2, SnI2, and SnBr2.

[0018] Preferably, the solvent includes at least one of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

[0019] More preferably, the solvent includes N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), wherein the volume ratio of DMF to DMSO is (3-6):1.

[0020] Preferably, the concentration of the self-assembled monolayer forming agent in the perovskite precursor solution is 0.01-1 mg / mL.

[0021] More preferably, the concentration of the self-assembly monolayer forming agent is 0.05-0.5 mg / mL.

[0022] Preferably, the concentration of the perovskite material in the perovskite precursor solution is 0.1-5 mol / L.

[0023] More preferably, the concentration of the perovskite material in the perovskite precursor solution is 0.5-2 mol / L.

[0024] Preferably, the concentration of the ionic liquid in the perovskite precursor solution is 0.1-2% (v / v).

[0025] More preferably, the concentration of the ionic liquid is 0.1-1% (v / v).

[0026] A second aspect of the present invention provides a perovskite thin film, which is prepared from the perovskite precursor solution described in the first aspect.

[0027] A third aspect of the present invention provides a method for preparing the perovskite thin film described in the second aspect, comprising the following steps: The perovskite precursor solution described in the first aspect is coated onto the hole transport layer and then annealed to obtain the perovskite thin film. Preferably, the annealing temperature for the annealing treatment is 100-150℃.

[0028] Preferably, the annealing time for the annealing process is 20-30 minutes.

[0029] A fourth aspect of the present invention provides a perovskite battery comprising the perovskite thin film described in the second aspect.

[0030] Preferably, it includes a hole transport layer, a perovskite absorber layer, an electron transport layer, a buffer layer, and an electrode layer arranged sequentially; wherein the perovskite absorber layer is the perovskite thin film described in the second aspect, or is prepared from the perovskite precursor solution described in the first aspect.

[0031] More preferably, the material of the hole transport layer includes spiro-OMeTAD, PTAA, and NiO. x At least one of PEDOT and PSS.

[0032] More preferably, the material of the electron transport layer includes at least one of fullerene (C60) and its derivatives, PCBM, SnO2, TiO2, and ZnO.

[0033] More preferably, the buffer layer is a SnO2 layer.

[0034] More preferably, the material of the electrode layer includes at least one of Ag and Cu.

[0035] More preferably, the method for preparing the perovskite solar cell includes: preparing a hole transport layer on a conductive substrate, depositing a perovskite absorber layer on the surface of the hole transport layer, and then sequentially depositing an electron transport layer, a buffer layer, and an electrode layer on the surface of the perovskite absorber layer to obtain the perovskite solar cell.

[0036] The beneficial effects of this invention are: This invention provides a perovskite precursor solution in which a self-assembled monolayer (SAM) forming agent and an ionic liquid are simultaneously doped. This provides the following advantages: (i) The dense monolayer formed by SAM on the surface and interface of the perovskite film effectively blocks the penetration of water molecules and oxygen, reducing hydrolysis and oxidation of the perovskite material and solving the problem of ionic liquid additives being easily affected, leading to a decrease in solar cell performance; (ii) The low saturated vapor pressure, high chemical stability, and thermal stability of the ionic liquid enable it to form a supporting structure within the perovskite film, inhibiting film cracking and ion migration caused by temperature changes, while protecting the SAM layer from being washed away by the perovskite solvent; (iii) In the co-doping strategy, SAM molecules are directly dispersed in the perovskite precursor solution and self-assemble synchronously with the perovskite crystallization process. This allows them to bind to the substrate and embed themselves within the perovskite film and grain boundaries, avoiding solvent erosion and achieving uniform modification across all dimensions. Furthermore, the ionic liquid can penetrate into the perovskite bulk phase, coordinating with bulk defects through cations (such as imidazole rings and guanidine groups), thereby enhancing the SAM layer's properties. It mainly modifies interface defects, and the two work together to achieve the dual function of "passivation of bulk defects + optimization of interface characteristics", covering all structural defects of perovskite thin films.

[0037] In summary, the perovskite precursor solution of this invention employs a co-doping strategy of SAM and ionic liquid, which can more comprehensively improve the efficiency and stability of perovskite solar cells compared to adding SAM / ionic liquid alone, while simplifying the process and laying the foundation for its commercial application. Detailed Implementation

[0038] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials used in the following embodiments can be obtained from conventional commercial channels or prepared and isolated through simple synthesis; unless otherwise specified, the processes employed are conventional processes in the art.

[0039] Example 1 This embodiment provides a perovskite solar cell, the structure of which comprises a substrate, a hole transport layer, a perovskite absorber layer, an electron transport layer, a buffer layer, and an electrode layer arranged sequentially. The fabrication methods for each layer of the perovskite solar cell are as follows: Step 1: Cut a 10×10cm piece 2 Glass was used as the substrate and ultrasonically cleaned in isopropanol (IPA) for 4 minutes. Physical vapor deposition was then performed using NiO. x NiO is prepared on an ITO substrate using a target material as raw material. x Hole transport layer. Then annealed in air at 200°C for 20 minutes. Allowed to cool naturally before use.

[0040] Step 2: Prepare a perovskite solution by weighing 52 mg CsI, 97 mg MABr, 504.3 mg FAI, 358.1 mg PbBr2, and 1460.5 mg PbI2 according to the stoichiometric ratio, and dissolving them in 4 mL of a mixed solvent of DMF:DMSO (V:V = 4:1) to obtain (FA... 0.73 MA 0.22 Cs 0.05 )Pb(I 0.82 Br 0.18 3. Perovskite material with a concentration of 1 mol / L was added to the perovskite solution along with 0.4 mg of Poly-4PACz (concentration of 0.1 mg / mL) and 0.4% of the perovskite solution volume of the ionic liquid BMIMTFSI. After stirring for 4 hours, the precursor solution was filtered through a 0.22 μm PTFE filter.

[0041] Step 3: For the preparation of the perovskite thin film, a slit coating process combined with VCD vacuuming was employed. The final coating process was obtained by optimizing the coating parameters, specifically: injection volume of 165 μl, injection speed of 6.2 μl / s, and pre-injection speed of 6 μl / s. A wet perovskite film was obtained through semi-automatic coating. The wet film was then placed in a vacuuming device, and the vacuum pressure was increased to 1000 Pa for 50 seconds. After vacuuming, the film was placed in an annealing furnace for annealing at 120℃ for 20 minutes, with a heating time of 100 seconds. After natural cooling, the desired perovskite thin film was obtained.

[0042] Step 4: Prepare 1.5 nm LiF using a thermal evaporation method. Dissolve the organic salt ethylenediamine dihydroiodide (EDAI) in IPA using an ultrasonic method; the optimal concentration is 0.4 mg / mL. Spin-coat the LiF-coated perovskite surface with the EDAI solution at 3000 rpm for 30 s, then anneal at 80 °C for 2 min. Allow the annealed film to cool naturally, forming a passivation layer on its surface.

[0043] Step 5: Evaporate 20 nm of C onto the perovskite film prepared in step 4. 60 Then, an atomic layer deposition (ALD) method was used to deposit a SnO2 buffer layer with a thickness of about 16 nm.

[0044] Step 6: Obtain a single-junction perovskite solar cell by vacuum evaporation of a 120 nm Ag electrode at a evaporation rate of 2.5 Å / s.

[0045] Step 7: Place the prepared perovskite solar cell in an annealing furnace for annealing at 120°C for 20 minutes.

[0046] Example 2 This embodiment provides a perovskite solar cell, which is prepared in a manner similar to that of Example 1. The difference is that 0.1 mg / mL Poly-4PACz and 0.7% of the perovskite solution volume of the ionic liquid BMIMTFSI are added to the perovskite solution and mixed to obtain a composite solution.

[0047] Example 3 This embodiment provides a perovskite solar cell, the preparation method of which is basically the same as that of Example 1, except that: 0.2 mg / mL Poly-4PACz and 0.7% of the perovskite solution volume of the ionic liquid BMIMTFSI are added to the perovskite solution, and the mixture is then used to obtain a composite solution.

[0048] Example 4 This embodiment provides a perovskite solar cell, the preparation method of which is basically the same as that of Example 1, except that: 0.3 mg / mL Poly-4PACz and 1% of the perovskite solution volume of the ionic liquid BMIMTFSI are added to the perovskite solution, and the mixture is then used to obtain a composite solution.

[0049] Example 5 This embodiment provides a method for preparing a perovskite solar cell, which is basically the same as that in Example 1, except that: 2 mg of 2-mercaptopropionic acid (concentration of 0.5 mg / mL) and 0.4% of the volume of the perovskite solution of the ionic liquid BMIMTFSI are added to the perovskite solution, and the mixture is then used to obtain a composite solution.

[0050] Comparative Example 1 This comparative example provides a perovskite solar cell, which is prepared in a manner that is basically the same as that in Example 1, except that only 0.4 mg of Poly-4PACz (concentration of 0.1 mg / mL) is added to the perovskite solution, and the ionic liquid BMIMTFSI is not added.

[0051] Comparative Example 2 This comparative example provides a perovskite solar cell, the preparation method of which is basically the same as that of Example 1, except that only 0.4% of the volume of the perovskite solution of ionic liquid is added to the perovskite solution, and Poly-4PACz is not added.

[0052] Application testing The perovskite solar cells of Examples 1-5 and Comparative Examples 1-2 were tested. The solar simulator light source intensity was calibrated to one solar radiation using a silicon reference cell calibrated with NREL correction, at an irradiance spectrum of AM 1.5G and a light intensity of 1000 W / m². 2 The solar cells were tested at a temperature of 25°C. The test results are shown in Figure 1. Table 1. Performance of perovskite solar cells in each embodiment and comparative example

[0053] Comparative data from the examples and comparative models show that, on the one hand, BMIMTFSI improves the uniformity of the Poly-4PACz-based SAM layer on the perovskite surface, reduces surface roughness, and decreases PbI2 impurity phases and halide vacancy defects; on the other hand, Poly-4PACz constructs a continuous hole transport channel through its conjugated backbone, and its phosphonic acid groups can strongly anchor to the ITO substrate to enhance the stability of the SAM layer. Both work synergistically in terms of interface and crystallinity. BMIMTFSI provides a flat substrate for perovskite growth, while Poly-4PACz restricts excessive grain growth, jointly forming a large-size, low-grain-density perovskite film. Regarding stability, the polymer coating of Poly-4PACz and the ionic bonding of BMIMTFSI synergistically block moisture penetration and inhibit perovskite decomposition and photodegradation. The following is the core principle of the performance improvement of the perovskite solar cell of this invention: (1) Synergistic defect passivation reduces non-radiative recombination. The cations of ionic liquids (such as guanidine salts like TMGBF4) contain multiple nitrogen atoms, which can react with uncoordinated Pb atoms in the perovskite phase. 2+ It forms stable coordination bonds, neutralizes positive charge defects, and reduces the recombination of charge carriers in the bulk phase trapped state; The phosphonic acid group of SAM (such as 2PACz, Me-4PACz) forms a covalent bond with the hydroxyl group of the substrate (such as ITO), while the terminal carbazole group bonds with the I-type surface of the perovskite. - Combined, it reduces the density of interface defect states.

[0054] (2) Regulate the crystallization process and optimize the microstructure of the thin film. Ionic liquids (such as imidazole-based HMTTSI) have high viscosity properties, which can slow down the evaporation rate of solvents (such as DMF) in perovskite precursors and inhibit grain agglomeration and defects caused by excessively rapid crystallization. SAM molecules provide uniform growth sites for perovskite crystals through directional alignment, guiding grains to grow along favorable charge transport directions and promoting the formation of large-size, low-grain-bound dense films.

[0055] (3) Construct a dual protection system to enhance long-term stability SAM forms a dense monolayer on the surface and interface of perovskite, and its hydrophobic groups can block the penetration of water molecules and oxygen, reducing the hydrolysis and oxidation rate of perovskite. The low vapor pressure and high chemical stability of ionic liquids can suppress ion migration in perovskites and reduce grain boundary cracking under temperature cycling.

[0056] In summary, the perovskite precursor solution of this invention employs a co-doping strategy of SAM and ionic liquid. Compared to adding SAM / ionic liquid alone, this strategy more comprehensively improves the efficiency and stability of perovskite solar cells while simplifying the process, laying the foundation for their commercial application. This synergistic effect ultimately drives a significant breakthrough in the performance of perovskite solar cells, greatly improving the stability of devices under high temperature, high humidity, and long-term illumination, providing key technical support for the commercialization of perovskite optoelectronic devices.

[0057] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A perovskite precursor solution, characterized in that, It includes the following components: perovskite material, self-assembled monolayer forming agent, ionic liquid and solvent.

2. The perovskite precursor solution according to claim 1, characterized in that, The self-assembled monolayer forming agent includes at least one of phosphonic acid self-assembled monolayer forming agents and mercapto self-assembled monolayer forming agents; Preferably, the phosphonic acid self-assembly monolayer forming agent includes at least one of (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid, polycarbazolephosphonic acid, (2-(9H-carbazole-9-yl)ethyl)phosphonic acid, (2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl)phosphonic acid, and [2-(9,10-dihydro-9,9-dimethylacridin-10-yl)ethyl]phosphonic acid; Preferably, the thiol-based self-assembled monolayer forming agent includes at least one of 2-mercaptopropionic acid and 3-mercaptopropionic acid.

3. The perovskite precursor solution according to claim 1, characterized in that, The ionic liquid includes at least one of imidazole ionic liquids, pyridine ionic liquids, quaternary ammonium ionic liquids, pyrrolidine ionic liquids, piperidine ionic liquids, functionalized ionic liquids, and guanidine salt ionic liquids.

4. The perovskite precursor solution according to claim 1, characterized in that, The perovskite material is selected from ABX3; wherein A is at least one of MA, MDA, FA, PEA, Cs, Rb and K; MA is CH3NH3; MDA is NH3CH2NH3; FA is NH2CHNH2; PEA is C8H9NH3; B is at least one of Pb, Sn and Ge; and X is at least one of F, Cl, Br and I.

5. The perovskite precursor solution according to claim 1, characterized in that, The solvent includes at least one of N,N-dimethylformamide and dimethyl sulfoxide.

6. The perovskite precursor solution according to claim 1, characterized in that, In the perovskite precursor solution, the concentration of the self-assembled monolayer forming agent is 0.01-1 mg / mL; And / or, the concentration of the ionic liquid is 0.1-2% (v / v).

7. A perovskite thin film, characterized in that, The perovskite film is prepared from the perovskite precursor solution according to any one of claims 1-6.

8. The method for preparing the perovskite thin film according to claim 7, characterized in that, Includes the following steps: The perovskite precursor solution according to any one of claims 1-6 is coated onto the hole transport layer and then annealed to obtain the perovskite thin film.

9. A perovskite battery, characterized in that, Includes the perovskite thin film as described in claim 7.

10. The perovskite solar cell according to claim 9, characterized in that, It includes a hole transport layer, a perovskite absorber layer, an electron transport layer, a buffer layer, and an electrode layer arranged sequentially; wherein the perovskite absorber layer is the perovskite thin film as described in claim 7, or is prepared from the perovskite precursor solution as described in any one of claims 1-6.

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