An in-situ passivation method of perovskite thin film, perovskite battery and preparation method thereof

Abstract

This invention provides an in-situ passivation method for perovskite thin films, a perovskite solar cell, and a method for preparing the same. The in-situ passivation method includes: preparing a perovskite precursor solution comprising formamidinium cations, divalent metal cations, halide anions, and fluorobenzylamine, wherein the content of fluorobenzylamine is 0.01% to 1% of the molar amount of formamidinium cations; coating the perovskite precursor solution and annealing it to crystallize the solution and allow the fluorobenzylamine and formamidinium cations to react in situ, forming an in-situ passivated perovskite thin film. In this application, fluorobenzylamine is used to in-situ passivate the formamidinium-containing perovskite system, achieving mutual promotion between the passivation and crystallization adjustment processes. Furthermore, in-situ passivation suppresses ion migration, allowing the high-quality thin film structure composed of large grains to be maintained during long-term operation, ultimately achieving high device stability.

Description

Technical Field

[0001] This application relates to the field of perovskite solar cells, and in particular to an in-situ passivation method for perovskite thin films, a perovskite solar cell, and a method for preparing the same. Background Technology

[0002] Perovskite solar cells have emerged as one of the most competitive candidates for next-generation photovoltaic technology due to their superior photoelectric properties, solution-processability, and potentially low manufacturing costs. Their certified power conversion efficiency (PCE) has rapidly increased from 3.8% in 2009 to the current 26.7%, demonstrating enormous application potential. However, to achieve commercial mass production and long-term application, their inherent stability issues and efficiency loss bottlenecks must still be addressed.

[0003] During the crystallization process, perovskite polycrystalline thin films form numerous grain boundaries and surfaces. Due to the discontinuity of the crystal structure, these regions become defect-rich areas, primarily including: 1) Lead-related defects: such as lead vacancies, lead interstitials, and antisite defects. These defects form deep energy levels in the band gap, becoming non-radiative recombination centers; 2) Halogen-related defects: such as iodine vacancies, which are the main cause of ion migration and p-type doping; 3) Organic cation defects: such as formamidinium vacancies, which disrupt the integrity of the crystal lattice. These defects, especially those located at grain boundaries and surfaces, act as non-radiative recombination centers for charge carriers, severely reducing carrier diffusion length and lifetime. Consequently, the open-circuit voltage (Voc) and fill factor (FF) of the device are significantly lower than their theoretical limits (i.e., the radiative recombination limit), constituting a core obstacle to efficiency improvement.

[0004] Besides efficiency losses, stability is another key challenge restricting the commercialization of PSCs. Its instability mainly manifests as: 1) Ion migration: Under illumination, electric fields, or thermal stress, ions (such as I) in the perovskite lattice migrate. - MA + ,FA + Ion migration is prone to occur. Ion migration not only directly leads to interfacial degradation and current-voltage hysteresis, but is also a major cause of halide phase separation. In mixed halogen (e.g., I / Br) wide-bandgap perovskites, Ig migration occurs under illumination. - and Br - Segregation of iodine forms a low-bandgap, iodine-rich region, which becomes the center of carrier recombination, leading to a continuous decline in open-circuit voltage and efficiency. Perovskite materials are extremely sensitive to water vapor and oxygen, and are prone to irreversible decomposition reactions such as hydrolysis and oxidation, generating non-photoactive products such as PbI2, which can lead to complete device failure.

[0005] To address these challenges, defect passivation has become an indispensable strategy for improving the performance of PSCs. Existing technologies primarily focus on surface passivation, which involves spin-coating or vapor-depositing passivating molecules, such as organic amines, onto the surface of a pre-formed perovskite film. However, existing amine-based passivation strategies have significant limitations; their mechanism relies on the interaction between amine groups (-NH2) and uncoordinated Pb on the perovskite film surface. 2+ Simple coordination between them or physical filling of vacancies results in limited interfacial bonding strength, which may fail under long-term operating stress and cannot provide a durable and stable passivation effect. Furthermore, ordinary amine materials lack additional protection mechanisms against environmental stress (especially moisture), and the improvement in the long-term stability of the device is difficult to meet commercial requirements.

[0006] Therefore, developing a passivation strategy based on a novel passivation mechanism that can simultaneously, efficiently, and persistently improve the efficiency and stability of perovskite solar cells has become a pressing technical challenge in this field.

[0007] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Summary of the Invention

[0008] The purpose of this invention is to provide a novel passivation strategy for perovskite thin films to achieve higher photoelectric conversion efficiency and long-term device stability.

[0009] To address the aforementioned problems, firstly, this application provides an in-situ passivation method for perovskite thin films, comprising the following steps:

[0010] A perovskite precursor solution is prepared, wherein the perovskite precursor solution comprises formamidinium cation, divalent metal cation, halide anion and fluorobenzylamine, wherein the content of fluorobenzylamine is 0.01% to 6% of the molar amount of formamidinium cation;

[0011] The perovskite precursor solution is coated and annealed to crystallize the perovskite precursor solution and allow the fluorobenzylamine and the formamidinium cation to react in situ, forming an in-situ passivated perovskite film.

[0012] In this application, fluorobenzylamine is used for in-situ passivation of a formamidinium-containing perovskite system, achieving a synergistic effect between passivation and crystallization adjustment. On one hand, the N-benzylformamidinium salt generated by the reaction and the ion-dipole or dipole-dipole interactions generated by the binding of fluorine atoms firmly anchor the reactants to grain boundaries and surfaces, forming a stable passivation layer. On the other hand, the NH3 molecules released during the reaction regulate the crystallization process, reducing the formation of small-sized grains and promoting the preferential growth of crystals by combining fluorine atoms with the perovskite precursor. This effectively increases the average crystal size and reduces the total grain boundary length per unit area, allowing more passivation molecules to concentrate at fewer grain boundaries. Furthermore, in-situ passivation suppresses ion migration, enabling the high-quality thin film structure composed of large grains to be maintained during long-term operation, ultimately achieving high device stability.

[0013] In this application, the content of fluorobenzylamine is 0.01% to 1% of the molar amount of formamidinium cation. Within this range, efficient passivation can be achieved without affecting device performance. If the content is too low (below 0.01%), insufficient passivation will result in a still high defect state density and significant nonradiative recombination; while if the content is too high (above 1%, especially above 6%), it will lead to the formation of low-dimensional phases, BnFA. + When large molecules aggregate at grain boundaries / surfaces, they do not participate in light absorption or carrier transport, which reduces the photoelectric conversion efficiency of the device.

[0014] The fluorobenzylamines include one or more of o-fluorobenzylamine, m-fluorobenzylamine, and p-fluorobenzylamine.

[0015] The fluorobenzylamine is o-fluorobenzylamine. In this scheme, the ortho-fluorine in o-fluorobenzylamine results in a large steric hindrance for the entire molecule, which is preferentially repelled to the grain boundaries and surface during crystallization, resulting in a more uniform and dense passivation layer, which further improves the passivation effect and stability. Moreover, the strong electron-withdrawing inductive effect of ortho-fluorine is transmitted along the σ bond, which reduces the electron cloud density of nitrogen on formamidinium, enhances its basicity, and strengthens its coordination ability.

[0016] The divalent metal cations include lead ions but not tin ions, and the halide anions include one or more of iodide ions, bromide ions, and chloride ions. This scheme is more suitable for lead-based formamidinium perovskite systems. Considering that the additives used in this scheme may undergo different chemical reactions in tin-based systems, generating byproduct complexes, they are not suitable for use in tin-based perovskites.

[0017] The annealing temperature for the annealing process is 90 ℃-110 ℃, and the annealing time is 15 min-20 min.

[0018] The content of the fluorobenzylamine is 0.1% to 1% of the molar amount of the formamidinium cation. This further provides a preferred addition range, which can achieve a balance between efficient passivation and device performance, avoiding insufficient passivation due to too low a content, or excessive addition leading to the accumulation of reaction products, the formation of new defects, and carrier transport problems.

[0019] The perovskite precursor solution comprises cesium ions, formamidinium ions, lead ions, iodide ions, bromide ions, and fluorobenzylamine; wherein the atomic ratio of cesium ions:formamidinium ions:lead ions:iodide ions:bromine ions is 0.2:0.8:1:2.4:0.6, and the content of fluorobenzylamine is 0.1% to 0.65% of the molar amount of formamidinium ions.

[0020] Secondly, this application also provides a method for preparing a perovskite solar cell, comprising:

[0021] A first carrier transport layer is formed on the surface of a transparent conductive substrate;

[0022] Using the in-situ passivation method for a perovskite thin film as described in any one of the first aspects, the perovskite thin film is formed on the surface of the first carrier transport layer to obtain a perovskite light-absorbing layer;

[0023] A second carrier transport layer and a metal electrode are sequentially formed on the perovskite light-absorbing layer;

[0024] The first carrier transport layer and the second carrier transport layer are respectively one of the electron transport layer and the hole transport layer.

[0025] A hole transport layer is formed on the surface of a transparent conductive substrate; the perovskite thin film is formed on the surface of the hole transport layer using the in-situ passivation method of any one of claims 1-7 to obtain a perovskite light-absorbing layer; a passivation layer is formed on the surface of the perovskite light-absorbing layer; an electron transport layer and a metal electrode are sequentially formed on the surface of the passivation layer.

[0026] Thirdly, this application also provides a perovskite solar cell, which is prepared according to the method for preparing a perovskite solar cell described in the second aspect.

[0027] Compared with existing technologies, the beneficial effects of this invention mainly include the following: This application proposes a novel passivation strategy and, through specific molecular design, achieves mutual promotion between in-situ passivation and crystallization adjustment processes, developing an innovative passivation technology with performance far exceeding traditional technologies. Unlike existing passivation treatments, this application utilizes, on the one hand, the N-benzylformamidinium salt generated by the reaction of fluorobenzylamine and formamidinium, and combines it with the ion-dipole or dipole-dipole interactions generated by fluorine atoms to firmly anchor the reactants to grain boundaries and surfaces, forming a stable passivation layer; on the other hand, it utilizes the NH3 molecules released during the reaction to regulate the crystallization process, reducing the formation of small-sized grains, and combining the interaction between fluorine atoms and perovskite precursors to promote preferred crystal growth, effectively increasing the average crystal size and reducing the total grain boundary length per unit area, allowing more passivation molecules to concentrate at fewer grain boundaries. Furthermore, fluorine on the benzene ring can enhance the coordination ability of nitrogen in formamidinium, reducing defects and mitigating perovskite ion migration. Meanwhile, the carbon-fluorine bond possesses high surface energy and strong hydrophobicity, enhancing the water stability of the film through passivation layers formed on the surface and at grain boundaries. After fluorine additive molecules accumulate on the surface / grain boundaries, their significant steric hindrance raises the migration barrier of ions at the interface, suppressing halide segregation and phase separation. Ultimately, in-situ passivation suppresses ion migration, allowing the high-quality thin film structure composed of large grains to be maintained during long-term operation, achieving high device stability. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 These are the molecular structural formulas of the three fluorobenzylamines in this application.

[0030] Figure 2 This is the 1H NMR spectrum of the reaction between fluorobenzylamine and formamidin hydroiodate in this application.

[0031] Figure 3 This is a reaction equation for a fluorobenzylamine and formamidin hydroiodate in this application.

[0032] Figure 4 The results show a comparison of the steady-state photoluminescence intensity of the perovskite thin films in Example 1 and Comparative Example 1 of this application.

[0033] Figure 5 The results show a comparison of the quantum yields of the perovskite thin films in Example 1 and Comparative Example 1 of this application.

[0034] Figure 6 The above are SEM comparison results of the perovskite thin films in Example 1 and Comparative Example 1 of this application.

[0035] Figure 7 The X-ray diffraction comparison results are shown for the perovskite thin films of Example 1 and Comparative Example 1 of this application.

[0036] Figure 8 The comparison results show the time-resolved photoluminescence decay curves of the perovskite thin films in Example 1 and Comparative Example 1 of this application.

[0037] Figure 9 The results show the IV curve comparison of the perovskite solar cells of Example 3 and Comparative Example 2 of this application.

[0038] Figure 10 This is a comparison of the maximum power point tracking test results of the perovskite solar cells in Example 3 and Comparative Example 2 of this application.

[0039] Figure 11 The results show the IV curve comparison of the perovskite solar cells of Examples 3 to 5 and Comparative Example 2 of this application.

[0040] Figure 12 The results are a comparison of the maximum power point tracking test results of the perovskite solar cells of Examples 3 to 5 and Comparative Example 2 of this application.

[0041] Figure 13 The results show the intensity comparison of steady-state photoluminescence of the perovskite thin films of Examples 1, 6 to 10 of this application.

[0042] Figure 14 The results show the comparison of IV curves for perovskite solar cells of Examples 3, 6 to 10 and Comparative Example 2 of this application. Detailed Implementation

[0043] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the accompanying drawings. The directional terms mentioned in the following embodiments, such as up, down, left, right, front, or back, are merely for reference to the accompanying drawings. Therefore, the directional terms used are for illustrative purposes and not for limiting the present invention.

[0044] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0045] The steps in the following embodiments do not correspond one-to-one with the contents of the invention.

[0046] Example 1

[0047] Embodiment 1 of the present invention provides an in-situ passivation method for perovskite thin films, comprising the following steps:

[0048] Step 1: Prepare the perovskite precursor solution;

[0049] In this first embodiment, the in-situ passivation method for the perovskite thin film is based on the existing solution-based perovskite thin film preparation process. In existing processes, the mainstream formation process for perovskite thin films (in perovskite solar cells, this film layer is also commonly referred to as the perovskite light-absorbing layer or perovskite absorption layer) involves coating (spin-coating or blade-coating) a precursor solution onto a substrate surface (which can be any suitable substrate; in perovskite solar cells, depending on the structure, it can be prepared on an electron transport layer or a hole transport layer) and then crystallizing it through annealing. This process is prior art and will not be elaborated upon here.

[0050] In existing technologies, passivation is an important means to improve the performance of perovskite thin films and perovskite solar cells. However, most existing passivation processes focus on interface passivation, which has limited effectiveness; moreover, the core mechanism of existing passivation processes relies on the interaction of passivating agents with uncoordinated Pb in the perovskite thin film. 2+ Simple coordination between components or physical filling of vacancies results in poor passivation and makes it difficult to meet the long-term stability requirements of devices.

[0051] In this first embodiment, a novel passivation strategy is proposed. By introducing a passivating agent during the preparation stage of the perovskite precursor solution, in-situ passivation of the perovskite film is achieved by utilizing the chemical reaction between the passivating agent and the formamidinium cation in the perovskite precursor solution during the crystallization process of the perovskite precursor solution.

[0052] Specifically, the perovskite precursor solution in this embodiment consists of two parts: a solvent and a solute. The solvent can be selected according to existing technology, such as N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and γ-butyrolactone (GBL).

[0053] The solvent comprises two types of substances: one is the precursor salt required for crystallization to form the perovskite material (ABX3 structure), and the other is an additive used to achieve in-situ passivation. For the perovskite precursor salt, existing technologies can be referenced, and this application only provides a brief introduction without further elaboration. As is well known, in the ABX3 structure of perovskite crystals, the A-site cation is a monovalent cation, typically including organic cations such as formamidinium ions (FA). +CH(NH2)2 + ), methylammonium ion (MA) + CH3NH3 + ), and inorganic cations: such as cesium ions (Cs ions). + ), rubidium ions (Rb + ), etc.; the B-site cation is a divalent metal cation, such as lead ion (Pb). 2+ ), tin ions (Sn) 2+ ) etc.; the X position is a halide anion, commonly an iodide ion (I). - ), bromide ions (Br) - ) and chloride ions (Cl - )wait.

[0054] In this first embodiment, a fluorobenzylamine compound with a specific structure was used as a passivating additive, with the following general structural formula: FR-NH2; where R is benzyl, and the substitution position of F (fluoro group) on the benzene ring includes ortho, meta, or para. A schematic diagram of the structure of fluorobenzylamine is shown below. Figure 1 As shown, the main difference between the three fluorobenzylamines lies in the position of fluorine on the benzene ring. Figure 1 In this context, 'a' represents ortho-fluorobenzylamine (i.e., ortho-fluorobenzylamine). Figure 1 In this context, 'b' represents meta-fluorobenzylamine (i.e., meta-fluorobenzylamine). Figure 1 In this context, 'c' represents para-fluorobenzylamine (i.e., p-fluorobenzylamine).

[0055] In this first embodiment, o-fluorobenzylamine is used when preparing the perovskite precursor solution; in other embodiments, when preparing the perovskite precursor solution, one or more of o-fluorobenzylamine, m-fluorobenzylamine, and p-fluorobenzylamine can be used.

[0056] It is understood that, unlike existing technologies, in this first embodiment, the added fluorobenzylamine does not exert its passivation effect in its original form (i.e., the existing passivation mechanism); instead, it utilizes the reaction between fluorobenzylamine and the formamidinium cation (FA) during the crystallization process of the precursor solution. + A rapid nucleophilic substitution reaction occurs, generating N-fluorobenzylformamidinium salt (F-BnFA) in situ. + (This can be used as a reference) Figure 2 and Figure 3 As shown. In Figure 2The chemical shift changes of formamidinium hydroiodate, o-fluorobenzylamine, and their mixture (formamidinium hydroiodate + o-fluorobenzylamine) are shown separately. In the mixed sample, the sharp peak of formamidinium hydroiodate at 7.84 ppm disappeared, replaced by a new set of peaks (7.66, 7.85, 7.96, 8.11 ppm). This indicates that the proton environment of formamidinium hydroiodate was significantly altered, meaning that formamidinium hydroiodate participated in the chemical reaction, and the new peaks represent the proton signal from the N-benzylformamidinium cation generated in solution. These results demonstrate that o-fluorobenzylamine underwent a chemical reaction in the formamidinium hydroiodate system, and the reaction product is stable in the solution phase. Figure 3 This presents the chemical equation for the reaction between o-fluorobenzylamine and formamidinium cations. This scheme utilizes F-BnFA generated from the reaction of fluorobenzylamine with formamidinium cations. + As an effective passivating agent, it is uniformly distributed on the grain boundaries and surface of the perovskite film, thereby achieving in-situ passivation of the perovskite film.

[0057] This technical solution is based on a deep understanding of the potential for utilizing and FA. + Based on chemical reactions, an innovative passivation technology with performance far exceeding traditional technologies has been developed through molecular design. Existing passivation mechanisms typically rely on two mechanisms: coordination with lead ions and coordination with A-site cations. Among these, coordination with lead ions (Pb...) 2+ The coordination of ) is a typical Lewis acid-base coordination, which belongs to the category of hard chemistry; while the "coordination" with the vacancy of the A-site cation is actually an ion exchange or filling reaction, which belongs to soft chemistry or size matching problem.

[0058] In this scheme, fluorobenzylamine molecules react with free formamidin cations (FA) in solution. + A chemical reaction occurs, producing a larger cation—N-benzylformamidinium salt (BnFA). + ), generated BnFA + The molecules selectively distribute themselves at the grain boundaries and surface of the perovskite film because these locations have the most defects (such as A-site vacancies), providing a site for the reaction. This is completely different from the two existing passivation mechanisms, and its passivation effect is more pronounced. Furthermore, in addition to passivation through reaction with formamidinium cations, the introduction of the fluorine atom (-F) in fluorobenzylamine adds a new mechanism, making its passivation mechanism even more efficient. Specifically, the fluorine atom is a very strong electron-withdrawing group, which allows F-BnFA to... + The molecules have a larger molecular dipole moment. This strong polarity allows the molecules to generate stronger ion-dipole or dipole-dipole interactions with charged defect sites (such as negatively charged lead dangling bonds), thus anchoring them more firmly to the interface and forming a more stable passivation layer.

[0059] Furthermore, in addition to passivation, the introduction of fluorobenzylamine can also regulate the crystallization process and improve the crystallinity of the film. Specifically, during the above reaction, NH3 molecules are released while N-benzylformamidinium salt is being generated. The presence of NH3 promotes the redissolution of small, unstable grains in the perovskite film during crystallization, allowing larger, stable grains to grow further, thereby increasing the grain size in the film and reducing the number of grain boundaries. At the same time, fluorine atoms (CF) can guide the perovskite crystals to grow more orderly through interaction with the perovskite precursor, thus obtaining a film with more pronounced preferred orientation and higher crystallinity.

[0060] The regulation of the crystallization process also has a converse effect on the passivation process, further improving the passivation effect. This is because high-quality crystallization means larger and more complete grains. This directly leads to a shorter total grain boundary length per unit area. At the same additive concentration, for passivation molecules, this means fewer and more concentrated highly active regions that need to be covered and passivated, making the passivation task simpler and more efficient. It is precisely because of the larger grains and fewer defects that the generated BnFA... + Molecules can then concentrate more efficiently at fewer grain boundaries to function effectively. Simultaneously, this effective passivation layer inhibits ion migration, allowing the high-quality thin-film structure composed of large grains to be maintained during long-term operation, ultimately achieving high device stability.

[0061] Understandably, this scheme is based on the crystallization process and formamidin cations (FA). + The passivation is achieved through the reaction, so it is necessary to ensure that the perovskite precursor solution formed contains at least formamidinium cations; on this basis, the A-site cation may be partially or not used, and other monovalent cations may be omitted; in addition, in order to achieve the crystallization of perovskite, other divalent metal cations and halide anions are also necessary, but their types / contents are not limited and can be determined by those skilled in the art.

[0062] In this application, to ensure sufficient passivation effect, it is necessary to ensure that the formamidin cation (FA) is present. + The proportion of the cation at the A-site is not less than 70% (in molar content), and the content of the added fluorobenzylamine is 0.01% to 6% of the molar amount of the formamidinium cation. Further, in other embodiments, the content of fluorobenzylamine is preferably 0.1% to 1.3% of the molar amount of the formamidinium cation; more preferably, the content of fluorobenzylamine is 0.1% to 0.65% of the molar amount of the formamidinium cation.

[0063] In this embodiment, the perovskite material formed corresponding to the perovskite precursor solution is Cs. 0.2 FA 0.8 Pb(I0.8 Br 0.2 )3, wherein the added fluorobenzylamine is o-fluorobenzylamine, and the content of the added o-fluorobenzylamine is 0.65% of the molar amount of formamidin cation.

[0064] Step 2: Apply perovskite precursor solution;

[0065] After preparing the perovskite precursor solution described in step 1, it can be coated onto the substrate surface. The specific coating process is not limited in this step. A feasible example is as follows: 60 μL of the perovskite precursor solution is dropped onto the substrate surface, and then a two-step spin coating method is used. The first spin coating parameters are a rotation speed of 1000 rpm, an acceleration of 500 rpm / s, and a spin coating time of 10 seconds; the second spin coating parameters are a rotation speed of 4000 rpm, an acceleration of 3000 rpm / s, and a spin coating time of 30 seconds; and 150 μL of chlorobenzene antisolvent is dropped at the 15th second before the end of the spin coating.

[0066] Step 3: Perform annealing and crystallization treatment to form an in-situ passivated perovskite film;

[0067] After completing step 2 above, the substrate and the titanium dioxide precursor solution coated thereon are annealed to crystallize the perovskite precursor solution and allow the fluorobenzylamine and formamidinium cations therein to react in situ, ultimately forming an in situ passivated perovskite film.

[0068] In this first embodiment, the annealing temperature for the crystallization treatment is 100 °C, and the annealing time is 10 minutes. In other embodiments, the annealing temperature for the annealing treatment is 90 °C-110 °C, and the annealing time is 15 min-20 min.

[0069] Example 2

[0070] In this second embodiment, a method for fabricating a perovskite solar cell is provided, comprising: forming a first carrier transport layer on the surface of a transparent conductive substrate; forming a perovskite thin film on the surface of the first carrier transport layer using an in-situ passivation method for a perovskite thin film as described in the first embodiment, thereby obtaining a perovskite light-absorbing layer; and sequentially forming a second carrier transport layer and a metal electrode on the perovskite light-absorbing layer; wherein the first carrier transport layer and the second carrier transport layer are one of an electron transport layer and a hole transport layer, respectively.

[0071] It can be understood that the main feature of the perovskite solar cell preparation method in this second embodiment is that the in-situ passivation method of the perovskite thin film in the first embodiment is introduced into the existing perovskite solar cell preparation process, that is, the in-situ passivation method of the perovskite thin film in the first embodiment is used to prepare the perovskite light-absorbing layer in the perovskite solar cell.

[0072] Existing perovskite solar cells include two structures: formal and inverted. The formal structure generally comprises a conductive glass layer, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer, and a metal electrode, stacked sequentially. The inverted structure generally comprises a conductive glass layer, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, and a metal electrode. The main difference between the two lies in the order in which the carrier transport layers (including the first and second carrier transport layers) are arranged on either side of the perovskite light-absorbing layer.

[0073] Specifically, in this second embodiment, taking the fabrication of an inverted perovskite solar cell as an example, the fabrication method includes the following steps (based on this application, the fabrication process of the formal structure solar cell is easily known to those skilled in the art simply by changing the fabrication order of the carrier transport layer, so it will not be described in detail in this application):

[0074] Step 1: Provide a transparent conductive substrate;

[0075] First, a transparent conductive substrate is provided and then cleaned. Commonly used transparent conductive substrates are either ITO or FTO. In this second embodiment, an indium tin oxide (ITO) substrate is used, which is then treated in a UV ozone cleaner for 15 minutes to remove surface impurities and improve wettability.

[0076] Step 2: Prepare the hole transport layer;

[0077] In this second embodiment, the hole transport layer is NiO. x The preparation process of the bilayer composite structure consisting of a NiO layer and a MeO-4PACZ layer is as follows: First, 10 mg / mL NiO is spin-coated onto the substrate. x 65 μL of solution (solvent: deionized water) was spin-coated at 2000 rpm for 30 seconds with an acceleration of 1000 rpm / s; then annealed at 150 °C for 15 minutes; followed by spin-coating 65 μL of 0.5 mg / mL MeO-4PACZ solution (solvent: ethanol) at 4000 rpm for 30 seconds with an acceleration of 4000 rpm / s, and then annealed at 100 °C for 10 minutes.

[0078] In other embodiments, the hole transport layer may be made of NiO. x Any one or several layers of Me-4PAC or MeO-4PACZ.

[0079] Step 3: Prepare the perovskite light-absorbing layer;

[0080] A perovskite thin film was formed on the surface of the hole transport layer using the in-situ passivation method described in Example 1, resulting in a perovskite light-absorbing layer. Specifically, 60 μL of the perovskite precursor solution prepared according to the method in Example 1 was dropped onto the hole transport layer, followed by a two-step spin coating process. The first spin coating parameters were 1000 rpm rotation speed and 500 rpm / s acceleration, with a spin coating time of 10 seconds. The second spin coating parameters were 4000 rpm rotation speed and 3000 rpm / s acceleration, with a spin coating time of 30 seconds. At the 15th second before the end of the spin coating, 150 μL of chlorobenzene antisolvent was dropped onto the perovskite film. After spin coating, the film was annealed at 100 °C for 10 minutes to allow the perovskite precursor solution to crystallize and for the fluorobenzylamine and formamidinium cations to react in situ, forming an in-situ passivated perovskite thin film, thus obtaining the perovskite light-absorbing layer.

[0081] Step 4: Prepare the passivation layer;

[0082] By preparing another passivation layer on the perovskite light-absorbing layer that has already undergone bulk passivation, the passivation effect can be further improved. It is understood that in the scheme of this application, step four is an optional process, and in other embodiments, this step may not be performed.

[0083] Specifically, in this second embodiment, the passivation layer is prepared as follows: 60 μL of 1 mg / mL EDAI solution (isopropanol as solvent) is spin-coated onto the perovskite light-absorbing layer for passivation treatment.

[0084] In other embodiments, the passivation layer can be any one or more of EDAI, PEAI, and PDADI.

[0085] Step 5: Fabrication of the electron transport layer:

[0086] Spin-coat 70 μL of 20 mg / mL isomethyl [6,6]-phenyl-C61-butyrate (i.e., PCBM solution, with chlorobenzene as solvent) onto the perovskite light-absorbing layer (or, if a passivation layer is prepared, on the surface of the passivation layer). The spin-coating speed is 2000 rpm, the time is 30 seconds, and the acceleration is 1500 rpm / s.

[0087] In other embodiments, the electron transport layer may be a tin oxide / C60 composite layer.

[0088] Step Six: Preparing the Metal Electrode:

[0089] In this embodiment, Ag is used as the electrode material, and the fabrication process is a metal vapor deposition process. Specifically, an aperture area of ​​0.0750 cm² is used. 2 The mask is placed on the top layer of glass, and then Ag with a thickness of 100 nm is deposited as a metal electrode.

[0090] In other embodiments, electrodes may also be made of other metallic materials such as copper.

[0091] Example 3

[0092] In this third embodiment, a perovskite battery is provided, which is prepared by a perovskite battery preparation method described in the second embodiment.

[0093] Example 4

[0094] In this fourth embodiment, an in-situ passivation method for perovskite thin films, a perovskite solar cell, and a method for preparing the same are provided. The in-situ passivation method for perovskite thin films is basically the same as the in-situ passivation method described in Example 1, with the main difference being that the fluorobenzylamine added to the prepared perovskite precursor solution is m-fluorobenzylamine.

[0095] This embodiment four also provides a method for preparing a perovskite solar cell, which is basically the same as the method for preparing a perovskite solar cell described in embodiment two above. The main difference is that when preparing the perovskite light-absorbing layer, an in-situ passivation method for a perovskite thin film as described in embodiment four is used to form a perovskite thin film on the surface of the first carrier transport layer.

[0096] This embodiment also provides a perovskite thin film, obtained according to an in-situ passivation method for a perovskite thin film as described in this embodiment.

[0097] This embodiment four also provides a perovskite battery, which is obtained according to the preparation method of a perovskite battery described in this embodiment four.

[0098] Example 5

[0099] In this fifth embodiment, an in-situ passivation method for perovskite thin films, a perovskite solar cell, and a method for preparing the same are provided. The technical solution of this fifth embodiment can be referred to in the fourth embodiment, the main difference being that the fluorobenzylamine added to the prepared perovskite precursor solution is p-fluorobenzylamine.

[0100] Example 6

[0101] In this sixth embodiment, an in-situ passivation method for perovskite thin films, a perovskite solar cell, and a method for preparing the same are provided. The technical solution of this sixth embodiment can be referred to in the fourth embodiment, the main difference being that the added fluorobenzylamine in the prepared perovskite precursor solution is o-fluorobenzylamine, and the content of the added o-fluorobenzylamine is 0.01% of the molar amount of formamidinium cation.

[0102] Example 7

[0103] In this seventh embodiment, an in-situ passivation method for perovskite thin films, a perovskite solar cell, and a method for preparing the same are provided. The technical solution of this seventh embodiment can be referred to in embodiment four, the main difference being that the fluorobenzylamine added to the prepared perovskite precursor solution is o-fluorobenzylamine, and the content of the added o-fluorobenzylamine is 0.1% of the molar amount of formamidinium cation.

[0104] Example 8

[0105] In this eighth embodiment, an in-situ passivation method for perovskite thin films, a perovskite solar cell, and a method for preparing the same are provided. The technical solution of this eighth embodiment can be referred to in embodiment four, the main difference being that the fluorobenzylamine added to the prepared perovskite precursor solution is o-fluorobenzylamine, and the content of the added o-fluorobenzylamine is 1% of the molar amount of formamidinium cation.

[0106] Example 9

[0107] In this ninth embodiment, an in-situ passivation method for perovskite thin films, a perovskite solar cell, and a method for preparing the same are provided. The technical solution of this ninth embodiment can be referred to in embodiment four, the main difference being that the added fluorobenzylamine in the prepared perovskite precursor solution is o-fluorobenzylamine, and the content of the added o-fluorobenzylamine is 1.3% of the molar amount of formamidinium cation.

[0108] Example 10

[0109] In this tenth embodiment, an in-situ passivation method for perovskite thin films, a perovskite solar cell, and a method for preparing the same are provided. The technical solution of this ninth embodiment can be referred to in this fourth embodiment, the main difference being that the added fluorobenzylamine in the prepared perovskite precursor solution is o-fluorobenzylamine, and the content of the added o-fluorobenzylamine is 6% of the molar amount of formamidinium cation.

[0110] Comparative Example 1

[0111] In this Comparative Example 1, a perovskite thin film is provided, the structure and preparation process of which are basically the same as those described in the above embodiments. The difference is that fluorobenzylamine is not added to the perovskite precursor solution used in the preparation of the perovskite thin film. That is, in this Comparative Example 1, the perovskite precursor solution is simply Cs. 0.2 FA 0.8 Pb(I 0.8 Br 0.2 3.

[0112] Comparative Example 2

[0113] In Comparative Example 2, a perovskite solar cell is provided, the structure and preparation process of which are basically the same as those described in the above examples. The difference is that when preparing the perovskite light-absorbing layer in the perovskite solar cell, fluorobenzylamine is not added to the perovskite precursor solution used. That is, in Comparative Example 2, the perovskite precursor solution is simply Cs. 0.2 FA 0.8 Pb(I 0.8 Br 0.2 3.

[0114] To illustrate the technical effects of this application, please refer to the references. Figures 4 to 14 As shown, the perovskite films obtained in Examples 1, 4 to 10 (referred to as Examples 1 and 4 to 10 in the figures below), the perovskite solar cells obtained in Examples 3, 4 to 10 (referred to as Examples 3 and 4 to 10 in the figures below), the perovskite films obtained in Comparative Example 1 (referred to as Comparative Example 1 in the figures below), and the perovskite solar cells obtained in Comparative Example 2 (referred to as Comparative Example 2 in the figures below) were subjected to comprehensive testing and analysis. The results are as follows.

[0115] Figure 4 The results show a comparison of the steady-state photoluminescence intensity of two perovskite thin films. It can be found that the steady-state photoluminescence intensity of the perovskite thin film in Example 1 is significantly higher, indicating that the nonradiative recombination of the perovskite thin film is effectively suppressed, the carrier lifetime is longer, and the material quality is improved.

[0116] Figure 5 The results comparing the quantum yields of two perovskite thin films are shown. It can be observed that the perovskite thin film in Example 1 has a significantly higher quantum yield, which also demonstrates that the introduction of additives effectively suppresses nonradiative recombination, extends carrier lifetime, reduces the material defect state density, and improves crystal quality.

[0117] Figure 6 The following are SEM comparison results of the two perovskite thin films. It can be observed that, compared to Comparative Example 1, the film in Example 1 has a significantly larger grain size and a more compact grain arrangement, with a significant reduction in porosity. This indicates that fluorobenzylamine effectively promotes grain growth, causing small grains to merge into larger grains and fill grain boundary voids. Larger grains reduce grain boundary scattering, which facilitates long-distance electron and hole transport and can increase current density.

[0118] Figure 7The X-ray diffraction results for the two perovskite films are shown. The diffraction peak intensity of Example 1 is significantly higher and sharper, indicating a significant improvement in the crystallinity of this perovskite film. Furthermore, the decrease in the lead iodide peak in Example 1 indicates that fluorobenzylamine promoted the full reaction between FAI and PbI2, reduced unreacted precursor residues, and improved the purity of the perovskite main phase, thus achieving the preparation of a high-purity, high-crystallinity, and low-defect perovskite film.

[0119] Figure 8 The comparison results of time-resolved photoluminescence decay curves are shown. The curve of Example 1 decays more slowly, maintaining a high intensity at 1000 ns, which directly corresponds to the suppression of nonradiative recombination and the extension of carrier lifetime, indicating that the film quality is improved.

[0120] Figure 9 The comparison results of the IV curves of two perovskite solar cells are shown. Based on the above test results, it can be found that the addition of fluorobenzylamine improves the performance of perovskite solar cells in multiple dimensions by optimizing crystal morphology (larger grains, denser structure), increasing crystallinity, and suppressing defect / non-radiative recombination. This results in the perovskite solar cell in Example 3 outperforming the perovskite solar cell obtained in Comparative Example 2 in all four core parameters: fill factor, short-circuit current density, open-circuit voltage, and photoelectric conversion efficiency.

[0121] Figure 10 The results of maximum power point tracking (MPPT) tests on two types of perovskite solar cells are shown. MPPT testing can track the maximum power output for an extended period under simulated real-world operating conditions (continuous illumination), quantitatively assessing its long-term stability. Compared to Comparative Example 2, the perovskite solar cell in Example 3 maintains approximately 80% of its initial efficiency after more than 1000 hours, while the perovskite solar cell in Comparative Example 2 degrades to below 60% of its initial efficiency in less than 300 hours, indicating a significant improvement in the stability of the perovskite solar cell in Example 3.

[0122] refer to Figure 11 The figures show the IV curve comparison results of perovskite solar cells with the same content (0.65%) of three fluorobenzylamines (o-fluorobenzylamine, m-fluorobenzylamine, and p-fluorobenzylamine). Based on the above test results, it can be found that the perovskite solar cell obtained by adding fluorobenzylamine is superior to the perovskite solar cell obtained in Comparative Example 2 in all four core parameters: fill factor, short-circuit current density, open-circuit voltage, and photoelectric conversion efficiency. Among the different types of fluorobenzylamines, o-fluorobenzylamine has the best improvement effect, showing a significant performance improvement compared to Comparative Example 2.

[0123] refer to Figure 12The results show a comparison of the maximum power point tracking (MPPT) of perovskite solar cells with the same amount (0.65%) of three fluorobenzylamines (o-fluorobenzylamine, m-fluorobenzylamine, and p-fluorobenzylamine). Based on these results, it can be seen that the long-term stability of the perovskite solar cells obtained by adding fluorobenzylamines is superior to that of the perovskite solar cells obtained in Comparative Example 2; among different types of fluorobenzylamines, o-fluorobenzylamine shows the best improvement effect.

[0124] Figure 13 The results show a comparison of the steady-state photoluminescence intensity of perovskite films with different concentrations (0.01% to 6%) of o-fluorobenzylamine. It can be observed that the steady-state photoluminescence intensity gradually increases with increasing o-fluorobenzylamine concentration, reaching its highest value at a concentration of 0.65%. This indicates that non-radiative recombination of the perovskite films obtained at these concentrations is effectively suppressed, carrier lifetime is extended, and material quality is improved. When the concentration continues to increase, the steady-state photoluminescence intensity begins to decrease, possibly because excessively high concentrations lead to the formation of low-dimensional phases, affecting the normal crystallization of the perovskite.

[0125] refer to Figure 14 The figures show the IV curve comparison results of perovskite solar cells with different contents (0.01% to 6%) of o-fluorobenzylamine. Combining the above test results, it can be found that within the content range of 0.01% to 1%, the corresponding perovskite solar cells outperform the perovskite solar cells obtained in Comparative Example 2 in all four core parameters: fill factor, short-circuit current density, open-circuit voltage, and photoelectric conversion efficiency. The figures show that the improvement effect gradually increases with increasing o-fluorobenzylamine concentration, achieving the highest photoelectric conversion efficiency at a concentration of 0.65%. Further increases in concentration may lead to the formation of low-dimensional phases, such as BnFA. + When macromolecules aggregate at grain boundaries / surfaces, they do not participate in light absorption or carrier transport, which reduces the photoelectric conversion efficiency of the device. At 1.3%, the photoelectric conversion efficiency is basically the same as that of Comparative Example 2. When the concentration is further increased to 6%, its photoelectric conversion efficiency is even lower than that of Comparative Example 2.

[0126] The common English terms or letters used in this invention for clarity of description are for illustrative purposes only and are not limiting interpretations or specific uses. They should not be used to limit the scope of protection of this invention based on their possible Chinese translations or specific letters.

[0127] It should also be noted that in this article, relational terms such as “first” and “second” are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

Claims

1. An in-situ passivation method for perovskite thin films, characterized in that, Includes the following steps: A perovskite precursor solution is prepared, wherein the perovskite precursor solution comprises formamidinium cation, divalent metal cation, halide anion and fluorobenzylamine, wherein the content of fluorobenzylamine is 0.01% to 1% of the molar amount of formamidinium cation; The perovskite precursor solution is coated and annealed to crystallize the perovskite precursor solution and allow the fluorobenzylamine and the formamidinium cation to react in situ, forming an in-situ passivated perovskite film.

2. The in-situ passivation method for perovskite thin films according to claim 1, characterized in that, The fluorobenzylamines include one or more of o-fluorobenzylamine, m-fluorobenzylamine, and p-fluorobenzylamine.

3. The in-situ passivation method for perovskite thin films according to claim 2, characterized in that, The fluorobenzylamine is o-fluorobenzylamine.

4. The in-situ passivation method for perovskite thin films according to claim 1, characterized in that, The divalent metal cations include lead ions but not tin ions, and the halogen anions include one or more of iodide ions, bromide ions, and chloride ions.

5. The in-situ passivation method for perovskite thin films according to claim 1, characterized in that, The annealing temperature for the annealing process is 90 ℃-110 ℃, and the annealing time is 15 min-20 min.

6. The in-situ passivation method for perovskite thin films according to claim 1, characterized in that, The content of the fluorobenzylamine is 0.1% to 1% of the molar amount of the formamidin cation.

7. The in-situ passivation method for perovskite thin films according to claim 4, characterized in that, The perovskite precursor solution includes cesium ions, formamidinium ions, lead ions, iodide ions, bromide ions, and fluorobenzylamine. The atomic ratio of cesium ion:formamidinium ion:lead ion:iodide ion:bromine ion is 0.2:0.8:1:2.4:0.6, and the content of fluorobenzylamine is 0.1% to 0.65% of the molar amount of formamidinium ion.

8. A method for preparing a perovskite solar cell, characterized in that, include: A first carrier transport layer is formed on the surface of a transparent conductive substrate; Using the in-situ passivation method for a perovskite thin film according to any one of claims 1-7, the perovskite thin film is formed on the surface of the first carrier transport layer to obtain a perovskite light-absorbing layer; A second carrier transport layer and a metal electrode are sequentially formed on the perovskite light-absorbing layer; The first carrier transport layer and the second carrier transport layer are respectively one of the electron transport layer and the hole transport layer.

9. The method for preparing a perovskite solar cell according to claim 8, characterized in that, A hole transport layer is formed on the surface of a transparent conductive substrate; Using the in-situ passivation method for a perovskite thin film according to any one of claims 1-7, the perovskite thin film is formed on the surface of the hole transport layer to obtain a perovskite light-absorbing layer; A passivation layer is formed on the surface of the perovskite light-absorbing layer; An electron transport layer and a metal electrode are sequentially formed on the surface of the passivation layer.

10. A perovskite solar cell, characterized in that, The perovskite solar cell is prepared according to the method described in claim 8 or 9.

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