Preparation method of perovskite thin film and application thereof

Abstract

The application relates to a preparation method of a perovskite film and application thereof, and the preparation method comprises the following steps: S1, preparing a perovskite precursor solution; the perovskite precursor solution comprises 0.005 M-0.4 M of an additive, and the additive comprises a sulfone group and / or a succinimide group; S2, applying the perovskite precursor solution to a substrate surface to form a wet film, and obtaining an intermediate film through a drying treatment; and S3, performing a multi-step annealing treatment on the intermediate film to obtain the perovskite film. Through the introduction of a specific additive into the perovskite precursor solution and the cooperation of a staged crystallization process, the application realizes fine regulation of a crystal growth process, significantly improves the crystallization quality, avoids the damage of residues to the performance and stability of devices, and provides a new preparation approach for preparing a perovskite solar cell with high efficiency and high stability.

Description

Technical Field

[0001] This invention relates to the field of perovskite thin film preparation technology, and specifically to a method for preparing perovskite thin films and their applications. Background Technology

[0002] Perovskite solar cells have become a research hotspot in next-generation thin-film photovoltaic technology due to their advantages such as rapid improvement in photoelectric conversion efficiency, relatively simple fabrication process, and low material cost. The quality of the perovskite photoactive layer (including crystallinity, grain size, orientation, compactness, and defect density) directly determines the device's photoelectric conversion efficiency and long-term operational stability. However, in the process of preparing perovskite thin films using solution methods, the crystallization kinetics are often extremely rapid and difficult to control, easily forming numerous grain boundaries, pinholes, and residual stress, leading to severe nonradiative recombination of charge carriers and material degradation. Therefore, additive engineering has been widely introduced, aiming to improve film quality and device performance by adding functional molecules to the precursor solution or during thin film treatment to regulate the crystallization rate, induce preferred orientation, and passivate grain boundaries and surface defects.

[0003] Currently, commonly used additives can be divided into the following two categories based on their physicochemical properties and volatility characteristics: Volatile co-solvent additives, such as dimethyl sulfoxide (DMSO) and N-methylpyrrolidone (NMP), can form moderately strong coordination bonds with lead ions to generate stable mesophase complexes, thereby effectively slowing down the nucleation and crystallization rate of perovskites, inhibiting pinhole formation, and improving film coverage. However, these additives typically have low boiling points (e.g., DMSO has a boiling point of 189 °C, but it volatilizes rapidly under conventional annealing conditions), escaping in large quantities from the system during the low-temperature pre-annealing stage (e.g., 50–100 °C). By the time the subsequent critical high-temperature crystallization growth stage (usually >100 °C) begins, the residual concentration of the additive is extremely low, making it difficult to continue effectively controlling grain growth, orientation evolution, and defect healing.

[0004] High-melting-point additives include some ionic liquids (such as 1-ethyl-3-methylimidazolium tetrafluoroborate), organic halide salts (such as MACl, FACl, PEAI), and macromolecular polymers (such as PMMA, PVP), whose melting points are typically above 200 °C, and some even above 300 °C. These additives are not easily volatilized during annealing and can persist throughout the entire crystallization process, thus more effectively controlling grain size, releasing lattice stress, passivating defects, and even inducing the formation of two-dimensional / three-dimensional heterostructures. However, their significant drawback is that a large amount remains inside the perovskite film or at the grain boundaries after annealing, and the amount of residue is extremely difficult to control precisely: if too much residue remains, it will hinder carrier transport, introduce non-radiative recombination centers, and directly lead to a decrease in the open-circuit voltage and fill factor of the device; more seriously, some of the residual high-melting-point additives are very prone to decomposition or migration under operating stress conditions such as light, high temperature and humidity, or electric field, which will not only lose the original passivation effect, but may also induce the degradation of perovskite materials, thereby seriously damaging the long-term operating stability of the device.

[0005] Therefore, there is an urgent need for a perovskite thin film preparation process that can balance high crystallinity quality and low residue, so as to achieve the preparation of high-efficiency and high-stability perovskite solar cells. Summary of the Invention

[0006] While existing volatile co-solvent additives can spontaneously dissipate, their dissipation window is too early, preventing them from continuously exerting their effects during the high-temperature crystallization stage. High-melting-point additives, although capable of controlling crystallization throughout the process, lack an active dissipation mechanism, leading to the accumulation of harmful residues. To address these issues, this invention provides a method for preparing perovskite thin films and its applications. By introducing specific additives into the perovskite precursor solution to synergistically induce a hierarchical crystallization process, precise control over the crystal growth process is achieved. This significantly improves crystallization quality while avoiding damage to device performance and stability from residues, providing a new preparation route for high-efficiency, high-stability perovskite solar cells.

[0007] Specifically, the following technical solutions are provided: The first aspect of this invention provides a method for preparing perovskite thin films, characterized by comprising the following steps: S1. Prepare perovskite precursor solution; The perovskite precursor solution contains an additive comprising sulfone and / or succinimide groups, the additive having a melting point of [missing information]. T m Meets 60℃≤ T m The temperature is ≤110 ℃, and the solubility of the additive in perovskite in the molten state at 110-130 ℃ is not less than 50 mg / g; The concentration of the additive in the perovskite precursor solution is 0.005 M-0.4 M; S2. The perovskite precursor solution is applied to the substrate surface to form a wet film, and then dried to obtain an intermediate film. S3. Perform multi-step annealing on the intermediate film to obtain the perovskite thin film; The multi-step annealing process includes sequentially performing a first annealing process, a second annealing process, and a third annealing process, wherein: The temperature of the first annealing treatment is 45 ℃-65 ℃, which is lower than the melting point of the additive. T m The time is 5-10 min to accelerate the evaporation of residual solvent and promote the initial film formation; The temperature of the second annealing treatment is ( T m +10)℃-( T m +20)℃, for 5-60 min. During this process, the heating temperature is slightly higher than the melting point of the additive, which can promote the perovskite phase transformation, realize local dissolution and recrystallization at the perovskite grain boundaries, and strengthen the perovskite crystallization. The third annealing treatment is carried out at a temperature of 135 ℃-160 ℃ for 5-45 min to remove residual additives, further enhance perovskite crystallization, and obtain perovskite films with high crystallinity and low defect state density.

[0008] This invention prepares perovskite films with both high crystallinity and low residue by introducing appropriate amounts of specific additives in conjunction with multi-step annealing processes, as detailed below: This invention selects specific additives that have a certain solubility for perovskite precursors and whose melting points are controlled within the range of 60-110 °C. These are small molecule compounds containing sulfone groups (dimethyl sulfone, diethyl sulfone) and / or succinimide groups (N-methylsuccinimide, N-hydroxysuccinimide), and the concentration of these additives in the perovskite precursor solution is controlled at 0.005 M-0.4 M. By introducing appropriate amounts of specific additives and forming a precise synergistic effect with a multi-step annealing process, precise control of the crystal growth process and extremely low additive residues are achieved: firstly, a first annealing treatment is performed (45-65 °C, below the melting point of the additives). T m (5-10 min), during which the additive remains solid and inert, only causing the main solvent (such as DMF) to evaporate rapidly, forming a metastable perovskite framework dominated by amorphous and microcrystalline states; then a second annealing treatment is performed (temperature rises to 5-10 min). T m +10~ T m+20 ℃, hold for 5-60 min), the annealing temperature is increased above the melting point of the additive. At this time, the additive changes from solid to molten liquid phase, forming a local wetting layer at the grain boundaries between perovskite particles. Since this liquid phase can moderately dissolve the perovskite components, the system enters the "dissolution-recrystallization" equilibrium. Based on the Ostwald ripening mechanism, atoms on the surface of smaller grains preferentially dissolve into the liquid phase and then diffuse and deposit onto the surface of larger grains, thereby significantly increasing the grain size, reducing the number of grain boundaries and defect density, and achieving high-quality secondary crystallization. Finally, a third annealing treatment is performed (135-160 ℃, 5-45 min). Taking advantage of the low compatibility between the additive and the perovskite lattice (molecular size and polarity mismatch) and its moderate volatility at high temperature, the additive molecules remaining at the grain boundaries or surface almost completely escape from the film, with extremely low residual amount (below the detection limit of current detection instruments).

[0009] The three-step annealing process described above, along with the melting point window, concentration, and functional group characteristics of the additives, are all indispensable: if the concentration is too low or the melting point is too high, it is difficult to form a continuous liquid phase medium; without the second step of liquid-phase mediated ripening, the grains cannot grow; and without the third step of high-temperature escape, residual additives will hinder carrier transport and impair stability. Through the synergistic effect of the aforementioned functional additives and the progressive annealing process of "low-temperature shaping - medium-temperature liquid-phase recrystallization - high-temperature purification," not only is the crystallinity, orientation, and compactness of the perovskite thin film significantly improved, but the problems of carrier transport impairment and stability reduction caused by the residue of traditional high-melting-point additives are also effectively avoided. This provides a novel and controllable material preparation route for the fabrication of high-efficiency, high-stability perovskite solar cells.

[0010] Further, in step S1, the additive is selected from one or more of dimethyl sulfone (MSM), diethyl sulfone (DS), N-methylsuccinimide (NMS), and N-hydroxysuccinimide (NHS).

[0011] Further, in step S1, the concentration of the additive in the perovskite precursor solution is preferably 0.01 M-0.3 M, such as 0.01 M, 0.05 M, 0.1 M, 0.15 M, 0.2 M, 0.25 M, 0.3 M, etc., including but not limited to the concentration values ​​listed above.

[0012] Furthermore, the perovskite film is a lead halide perovskite film with the chemical formula APbX3, wherein A is selected from one or more of formamidinium (FA), methylamine (MA) and cesium (Cs), and X is a halogen, such as I, Br, or Cl.

[0013] Preferably, the molar ratio of lead ions to additives in the perovskite precursor solution is (3.75-300):1, more preferably (5-150):1, for example, any molar ratio among 5:1-20:1, 30:1-50:1, 60:1-100:1, and 110:1-140:1.

[0014] Further, in step S1, the perovskite precursor salt and additives are dissolved in a solvent to obtain a clear perovskite precursor solution; the perovskite precursor salt includes at least two of formamidinium hydroiodate, lead iodide, methylamine hydrobromide, cesium iodide, lead bromide, lead chloride, and methylamine hydrochloride; the solvent is selected from one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and γ-valerol (GVL).

[0015] Furthermore, in step S2, the application method includes, but is not limited to, spin coating, scraping coating, printing, or inkjet printing.

[0016] Further, in step S2, the drying process specifically involves: placing the substrate with the wet film on a cold plate for cooling, and then obtaining an intermediate film through vacuum flash evaporation; preferably, the temperature of the cold plate is -20 ℃ to 0 ℃, for example -6 ℃, and the cooling time is 20-40 s; the vacuum degree of the vacuum flash evaporation is 0.1-20 Pa, and the time is 40-60 s.

[0017] In some preferred embodiments, the perovskite precursor solution is spin-coated onto a transparent conductive substrate (such as FTO, ITO, etc.) to form a uniform wet film; the substrate with the wet film is then quickly placed on a pre-cooled cold plate for cooling treatment, and then the cooled wet film is immediately transferred to a vacuum chamber for rapid vacuum treatment (e.g., reaching the target vacuum level in 5 seconds). Under vacuum, the solvent in the wet film evaporates in an orderly manner, resulting in an intermediate film.

[0018] A second aspect of the present invention provides a perovskite thin film prepared by the preparation method described in the first aspect.

[0019] A third aspect of the present invention provides a perovskite solar cell device comprising the perovskite thin film described in the second aspect.

[0020] Furthermore, the perovskite solar cell device is a pin-type (reverse) perovskite solar cell device or a nip-type (positive) perovskite solar cell device.

[0021] In some preferred embodiments, the pin-type perovskite solar cell device includes a transparent conductive substrate, a hole transport layer, a perovskite thin film layer, C60, SnO2, and a silver electrode stacked sequentially; the nip-type perovskite solar cell device includes a transparent conductive substrate, an electron transport layer, a perovskite thin film, a hole transport layer, and a gold electrode stacked sequentially.

[0022] The beneficial effects of this invention are: 1. This invention introduces functional additives containing sulfone groups and / or succinimide groups, with melting points controlled within the range of 60-110 ℃, and combines this with "low-temperature setting (45-65 ℃) - medium-temperature liquid-phase mediated secondary crystallization" (…). T m +10~ T m The three-step annealing process of "+20 ℃ - high-temperature purification (135-160 ℃)" enables precise hierarchical control of the perovskite crystallization process. This method not only offers strong process controllability and extremely low additive residue, avoiding the negative effects of traditional high-melting-point additives, but also exhibits excellent cross-system and cross-structure versatility: it is applicable to both conventional bandgap perovskites and can directly prepare high-quality wide bandgap (e.g., 1.68 eV) films; it has also been successfully applied to both inverted (pin) and normal (nip) device structures without requiring redesign of the process for different systems.

[0023] 2. The perovskite thin film prepared by the method provided by this invention not only exhibits significantly improved crystallinity and markedly enhanced X-ray diffraction peaks, but also a substantial reduction in defect state density and a significant increase in photoluminescence intensity. This is due to the secondary crystallization driven by Ostwald ripening at the grain boundaries caused by the melting of additives into a liquid phase during medium-temperature annealing. This results in the dissolution of small grains, the growth of large grains, a sharp reduction in the number of grain boundaries, release of intragranular stress, and filling of pinholes and voids, thereby forming a high-crystallinity, high-density, and low-defect high-quality thin film.

[0024] 3. The perovskite solar cells constructed using the perovskite thin films prepared by the above method exhibit excellent photoelectric conversion efficiency: even in a small area (0.058 cm²) of inverted structure... 2 The highest efficiency achieved in the device was 27.22%, and the upright structure of the same area also achieved an efficiency of 26.73%, verifying the structural versatility. More importantly, when the effective battery area increased to 1.01 cm²... 2At the same time, the efficiency remains as high as 26.50%, demonstrating good potential for large-scale fabrication. Furthermore, the 1.68 eV wide-bandgap perovskite solar cell fabricated using this process achieves an efficiency of 23.87%, laying a crucial material and technological foundation for the subsequent construction of high-efficiency tandem solar cells. In summary, this invention provides a practical material and process route for high-efficiency, high-stability, and large-area fabrication of perovskite photovoltaic devices. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a conventional annealing process (a) and a graded crystallization annealing process of the present invention (b); Figure 2 Digital photographs of perovskite FAPbI3 before and after heating at 120 °C with MSM and MPS, respectively. Figure 3 Cross-sectional images of the perovskite films prepared in Comparative Example 1, Example 1 and Comparative Example 3 using a scanning electron microscope (SEM). Figure 4 XRD patterns of the perovskite films prepared in Comparative Example 1 and Example 1; Figure 5 Photoluminescence (PL) spectra of the perovskite thin films prepared in Comparative Example 1 and Example 1; Figure 6 Space charge confinement current (SCLC) curves of pure hole structure (FTO / hole transport layer / perovskite layer / hole transport layer / Ag) devices constructed from perovskite thin films prepared in Comparative Example 1 and Example 1; Figure 7 Perovskite solar cells prepared for different embodiments and comparative examples JV The curve, where a corresponds to an area of ​​0.058 cm² prepared in Example 1. 2 The perovskite solar cell, b is the one prepared in Example 2 with an area of ​​0.058 cm². 2 The perovskite solar cell, c, is the one prepared in Example 3 with an area of ​​0.058 cm². 2 The perovskite solar cell, d, has an area of ​​0.058 cm² prepared in Example 4. 2 The perovskite solar cell, e, is the one with an area of ​​0.058 cm² prepared in Comparative Example 1. 2 The perovskite solar cell, f is the one prepared in Comparative Example 2 with an area of ​​0.058 cm². 2 The perovskite solar cell, g represents Comparative Example 3, has an area of ​​0.058 cm². 2 The perovskite solar cell, h is the area of ​​0.058 cm² prepared in Comparative Example 4. 2 The perovskite solar cell, i is the one prepared in Example 1 with an area of ​​1.01 cm².2 Perovskite solar cells.

[0026] Figure 8 The graph shows the stability of photoelectric conversion efficiency of the perovskite solar cells with a band gap of 1.53 eV prepared in Example 1 and Comparative Example 1 after heating at 85 °C for 1000 hours in an N2 environment. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The terms “comprising” or “including” used in this invention may also be replaced with the closed form “is” or “consisting of”.

[0029] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the data analysis is performed using conventional statistical analysis methods. For any specific techniques or conditions not specified in the examples, the techniques or conditions described in the literature in this field or the product instructions shall be followed. Unless otherwise specified, the reagents and materials mentioned can be obtained commercially or prepared by known methods. Example 1

[0030] This embodiment relates to the fabrication of a 1.53 eV bandgap inverted (pin) perovskite solar cell, as detailed below: (1) Preparation of precursor solution: In a glove box, 1.425 M formamidin hydroiodide (FAI), 0.075 M cesium iodide (CsI), 1.575 M lead iodide (PbI2), 0.3 M methylamine hydrochloride (MACl) and 0.3 M dimethyl sulfone (MSM) were dissolved in DMF and stirred to obtain perovskite precursor solution.

[0031] (2) Battery fabrication: First, the FTO substrate was pretreated by ultrasonically cleaning it in detergent, deionized water, acetone, and isopropanol (IPA) for 20 minutes each, followed by drying with nitrogen gas and UV-Ozone treatment for 20 minutes. Then, it was transferred to a glove box filled with nitrogen. Inside the glove box, a hole transport layer was prepared on the FTO substrate by spin coating. Specifically, an ethanol solution of [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid (Me-4PACz) and [2-(9H-carbazole-9-yl)ethyl]phosphonic acid (2PACz) (concentration 0.5 mg / mL, mass ratio 2:1) was spin-coated at 3000 rpm for 30 seconds, and then annealed at 100 °C for 10 minutes.

[0032] Next, a perovskite precursor solution was deposited using a two-step spin-coating process: first, spin-coating at 2000 rpm for 10 seconds, then accelerating to 5000 rpm at 1000 rpm / s and spin-coating for 7 seconds. Immediately after spin-coating, the substrate was transferred to a self-made vacuum flash evaporation system and cooled on a cold plate at -6 °C for 40 seconds. Subsequently, the chamber pressure was rapidly reduced to 5 Pa within 5 seconds and maintained at this vacuum level for 40 seconds. The treated film was then annealed on a hot plate: 55 °C for 5 min; 125 °C for 40 min; and 155 °C for 10 min to form a perovskite film.

[0033] After the film cooled to room temperature, surface passivation was performed: a solution of piperazine hydroiodide (PI) in isopropanol (concentration 0.3 mg / mL) was spin-coated at 4500 rpm for 30 seconds, followed by annealing at 100 °C for 5 minutes. To complete the device fabrication, a 20 nm thick C60 layer was first deposited by thermal evaporation at a rate of 0.2 Å / s. Subsequently, a 20 nm thick SnO2 layer was deposited at 80 °C using a atomic layer deposition (ALD) system with tetratetra(dimethylamino)tin (IV) and deionized water as precursors. Finally, a 140 nm thick silver (Ag) layer was deposited by thermal evaporation as the top electrode. A perovskite solar cell with a bandgap of 1.53 eV was finally fabricated.

[0034] The additive MSM used in this embodiment was mixed with FAPbI3 at a mass ratio of 10:1, and then heated to 120 °C. Figure 2 As shown, a clear solution is formed, which also indicates that MSM is molten and can dissolve perovskite at this temperature.

[0035] The scanning electron microscope (SEM) cross-sectional image of the perovskite thin film prepared in this embodiment is shown below. Figure 3 As shown in the figure, the perovskite thin film prepared in this embodiment has no pores at the interface and is very dense.

[0036] The XRD pattern of the perovskite thin film prepared in this embodiment is shown below. Figure 4 As shown in the figure, compared with the control group without MSM, the perovskite film prepared in this embodiment has a stronger perovskite diffraction signal and a significantly improved crystallinity.

[0037] The photoluminescence (PL) spectrum of the perovskite thin film prepared in this embodiment is as follows: Figure 5 As shown in the figure, the PL luminescence intensity of the perovskite thin film prepared in this embodiment is significantly enhanced, indicating that its non-radiative recombination is suppressed.

[0038] Furthermore, the space charge confinement current (SCLC) curve of the pure hole structure (FTO / hole transport layer / perovskite layer / hole transport layer / Ag) device constructed from the perovskite thin film prepared in this embodiment is shown in the figure below. Figure 6 As shown in the figure, the perovskite thin film prepared in this embodiment has a low defect density.

[0039] The power conversion efficiency (PCE) and short-circuit current density of the 1.53 eV bandgap inverted perovskite solar cell prepared in this embodiment are measured. J sc ), open circuit voltage ( V oc The photoelectric properties, including fill factor (FF), were tested, and the test results are as follows: Figure 7 a, Figure 7 As shown in i and Table 1: Small areas (0.058 cm²) prepared using the method described above in this embodiment. 2 The photoelectric conversion efficiency of perovskite solar cells can reach up to 27.22%, and the short-circuit current density is 26.44 mA / cm². 2 The open-circuit voltage is 1.195 V, and the fill factor is 0.8618; and the large-area fabrication (1.01 cm²) is scaled up. 2 The perovskite solar cell still achieves a photoelectric conversion efficiency of up to 26.50%, which is currently the highest efficiency for perovskite solar cells of this size, with a short-circuit current density of 26.09 mA / cm². 2 The open-circuit voltage is 1.206 V and the fill factor is 0.8423.

[0040] The inverse perovskite solar cell with a bandgap of 1.53 eV prepared in this embodiment also exhibits good stability: after being heated at 85 °C for 1000 hours in an N2 environment, its efficiency still retains 90.8% of the initial value. Figure 8 As shown. Example 2

[0041] This embodiment relates to the fabrication of an inverse perovskite solar cell with a bandgap of 1.53 eV, and differs from Embodiment 1 only in that: (1) Replace MSM with an equimolar amount of DS, and all other operations are the same; (2) The heat annealing procedure is: 55 ℃, 5 min; 85 ℃, 40 min; 155 ℃, 10 min, and the rest of the operation is the same.

[0042] The photoelectric conversion efficiency, short-circuit current density, open-circuit voltage, and fill factor of the 1.53 eV bandgap inverse perovskite solar cell prepared in this embodiment were tested. The test results are as follows: Figure 7 b and Table 1 show: the area is 0.058 cm². 2 The perovskite solar cells exhibit a photoelectric conversion efficiency as high as 27.08% and a short-circuit current density of 26.50 mA / cm². 2 The open-circuit voltage is 1.193 V and the fill factor is 0.8565. Example 3

[0043] This embodiment relates to the fabrication of an inverted perovskite solar cell with a bandgap of 1.53 eV, and differs from Embodiment 1 only in that: (1) Replace the 0.3 M M M M with the 0.1 M NMS, and keep all other operations the same; (2) The heat annealing procedure is: 55 ℃, 5 min; 80 ℃, 50 min; 155 ℃, 10 min, and the rest of the operation is the same.

[0044] The photoelectric conversion efficiency, short-circuit current density, open-circuit voltage, and fill factor of the 1.53 eV bandgap inverse perovskite solar cell prepared in this embodiment were tested. The test results are as follows: Figure 7 c, as shown in Table 1, has an area of ​​0.058 cm². 2 The perovskite solar cells exhibit a photoelectric conversion efficiency as high as 26.75% and a short-circuit current density of 26.31 mA / cm². 2 The open-circuit voltage is 1.188 V and the fill factor is 0.8560. Example 4

[0045] This embodiment relates to the fabrication of an inverse perovskite solar cell with a bandgap of 1.53 eV, and differs from Embodiment 1 only in that: (1) Replace the 0.3 M ... (2) The heat annealing program is: 55 ℃, 5 min; 110 ℃, 50 min; 155 ℃, 10 min, and the rest of the operation is the same.

[0046] The photoelectric conversion efficiency, short-circuit current density, open-circuit voltage, and fill factor of the 1.53 eV bandgap inverse perovskite solar cell prepared in this embodiment were tested. The test results are as follows: Figure 7 As shown in Table 1, d has an area of ​​0.058 cm². 2 The perovskite solar cells exhibit a photoelectric conversion efficiency as high as 27.01% and a short-circuit current density of 26.41 mA / cm². 2 The open-circuit voltage is 1.196 V and the fill factor is 0.8552. Example 5

[0047] This embodiment relates to the fabrication of an inverse perovskite solar cell with a bandgap of 1.68 eV, and differs from Embodiment 1 only in that: (1) Preparation of precursor solution: 1.12 M formamidine hydroiodide (FAI), 0.07 M cesium iodide (CsI), 1.05 M lead iodide (PbI2), 0.21 M methylamine hydrobromide (MABr), 0.42 M lead bromide (PbBr2) and 0.01 M NHS were dissolved in DMF and stirred to obtain perovskite precursor solution.

[0048] (2) The heat annealing procedure is: 55 ℃, 5 min; 110 ℃, 20 min; 135 ℃, 10 min, and the rest of the operation is the same.

[0049] The photoelectric conversion efficiency, short-circuit current density, open-circuit voltage, and fill factor of the 1.68 eV bandgap inverse perovskite solar cell prepared in this embodiment were tested. The test results are shown in Table 1: (Area: 0.058 cm²) 2 The perovskite solar cells exhibit a photoelectric conversion efficiency as high as 23.87% and a short-circuit current density of 22.03 mA / cm². 2 The open-circuit voltage is 1.273 V and the fill factor is 0.8512. Example 6

[0050] This embodiment relates to the fabrication of a 1.53 eV bandgap upright (nip) perovskite solar cell, which differs from Embodiment 1 only in that the solar cell structure is different. (1) Consistent with step (1) of Example 1; (2) The FTO conductive substrate was ultrasonically cleaned in detergent, deionized water, acetone and isopropanol for 20 minutes each, dried with nitrogen and treated with ultraviolet-ozone for 20 minutes, then spin-coated with SnO2 dispersion and annealed at 150 °C for 30 minutes.

[0051] The substrate was then transferred to a nitrogen-filled glove box, where a two-step perovskite precursor solution was deposited: first, spin-coating at 2000 rpm for 10 seconds, followed by an acceleration of 1000 rpm / s to 5000 rpm and spin-coating for 7 seconds. Immediately after spin-coating, the substrate was transferred to a self-made vacuum flash evaporation system and cooled on a cold plate at -6 °C for 40 seconds. The chamber pressure was then rapidly reduced to between 0.1 Pa and 10 Pa within 5 seconds and maintained at this vacuum level for 40 seconds. The treated film was then annealed on a hot plate: 55 °C for 5 min; 125 °C for 40 min; and 155 °C for 10 min to form a perovskite film.

[0052] After natural cooling to room temperature, a surface passivation layer was prepared by spin-coating a PEAI isopropanol solution (5 mg / mL, spin-coated at 4500 rpm for 30 seconds) onto the surface. A hole transport layer was then prepared by spin-coating a 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (Spiro-OMeTAD) solution (72.3 mg of spiro-OMeTAD dissolved in 1 mL of chlorobenzene, followed by the addition of 28.8 μL of 4-tert-butylpyridine and 17.5 μL of lithium bis(trifluoromethanesulfonyl)imine (Li-TFSI) solution (520 mg of Li-TFSI dissolved in 1 mL of acetonitrile), spin-coated at 3000 rpm for 30 seconds). Finally, a 100 nm thick gold (Au) layer was deposited as the top electrode using a thermal evaporation process, resulting in a perovskite solar cell with a bandgap of 1.53 eV in an upright structure.

[0053] The photoelectric performance of the upright perovskite solar cell with a bandgap of 1.53 eV prepared in this embodiment was tested, and the detailed test results are shown in Table 1. The effective test area was 0.058 cm². 2 Under these conditions, the device exhibits excellent photovoltaic performance: its photoelectric conversion efficiency reaches 26.73%, and its short-circuit current density is 26.38 mA / cm². 2 The open-circuit voltage reaches 1.185 V, and the fill factor is 0.8550. Comparative Example 1

[0054] This comparative example relates to the preparation of an inverted perovskite solar cell with a bandgap of 1.53 eV. The only difference from Example 1 is that no additives were added to the precursor solution, and a conventional annealing process was used (125 ℃, 40 min; 155 ℃, 10 min). All other operations were the same, and the corresponding perovskite solar cell with a bandgap of 1.53 eV was prepared.

[0055] The photoelectric conversion efficiency, short-circuit current density, open-circuit voltage, and fill factor of the 1.53 eV bandgap inverse perovskite solar cell prepared in this comparative example were tested. The test results are as follows: Figure 7 e corresponds to the area shown in Table 1: 0.058 cm² 2 The perovskite solar cell exhibits a photoelectric conversion efficiency of 26.22% and a short-circuit current density of 26.38 mA / cm². 2 The open-circuit voltage is 1.180 V and the fill factor is 0.8422.

[0056] The inverse perovskite solar cell with a bandgap of 1.53 eV prepared in this comparative example exhibits poor stability: after heating at 85 °C for 1000 hours in an N2 environment, its efficiency only retains 79.6% of the initial value. Figure 8 As shown. Comparative Example 2

[0057] This comparative example relates to the fabrication of an inverted perovskite solar cell with a bandgap of 1.53 eV, and differs from Example 1 only in that: (1) Replace MSM with an equimolar amount of DMSO, and keep all other operations the same; (2) The heat annealing procedure is: 55 ℃, 5 min; 100 ℃, 50 min; 155 ℃, 10 min, and the rest of the operation is the same.

[0058] The photoelectric conversion efficiency, short-circuit current density, open-circuit voltage, and fill factor of the 1.53 eV bandgap inverse perovskite solar cell prepared in this comparative example were tested. The test results are as follows: Figure 7 f corresponds to the area shown in Table 1: 0.058 cm² 2 The perovskite solar cell exhibits a photoelectric conversion efficiency of 25.68% and a short-circuit current density of 26.30 mA / cm². 2 The open-circuit voltage is 1.186 V and the fill factor is 0.8230. Comparative Example 3

[0059] This comparative example relates to the fabrication of an inverted perovskite solar cell with a bandgap of 1.53 eV, and differs from Example 1 only in that: (1) Replace MSM with an equimolar amount of sulfone benzene (MPS), and all other operations are the same; (2) The heat annealing procedure is: 55 ℃, 5 min; 100 ℃, 50 min; 155 ℃, 10 min, and the rest of the operation is the same.

[0060] The additive MPS used in this comparative example was mixed with FAPbI3 at a mass ratio of 10:1, and then heated to 120 °C. Figure 2 As shown, while MPS can melt at this temperature, it cannot dissolve perovskite. (Combined) Figure 3 The SEM cross-sectional images show that the film prepared with this additive has obvious pores inside and poor contact with the buried interface of the substrate.

[0061] The photoelectric conversion efficiency, short-circuit current density, open-circuit voltage, and fill factor of the 1.53 eV bandgap inverse perovskite solar cell prepared in this comparative example were tested. The test results are as follows: Figure 7 g corresponds to the area shown in Table 1: 0.058 cm² 2 The perovskite solar cell exhibits a photoelectric conversion efficiency of 24.01% and a short-circuit current density of 25.35 mA / cm². 2 The open-circuit voltage is 1.175 V and the fill factor is 0.8061. Comparative Example 4

[0062] This comparative example relates to the fabrication of an inverted perovskite solar cell with a bandgap of 1.53 eV. The only difference from Example 1 is that 0.01 M mercaptobenzoic acid (4-MBA) is used instead of 0.3 M M MSM. All other operations are the same.

[0063] The photoelectric conversion efficiency, short-circuit current density, open-circuit voltage, and fill factor of the 1.53 eV bandgap inverse perovskite solar cell prepared in this comparative example were tested. The test results are as follows: Figure 7 h corresponds to the area shown in Table 1: 0.058 cm² 2 The perovskite solar cell exhibits a photoelectric conversion efficiency of 26.39% and a short-circuit current density of 26.27 mA / cm². 2 The open-circuit voltage is 1.191 V, and the fill factor is 0.8434. Since 125 °C is much lower than the melting point of 4-MBA (210 °C), the additive cannot melt to form a liquid phase to mediate secondary crystallization in the second stage of annealing, and therefore the device performance is not as good as in Example 1. Comparative Example 5

[0064] This comparative example relates to the fabrication of an inverted perovskite solar cell with a bandgap of 1.53 eV. The only difference from Example 1 is that there is no first-stage annealing process. The thermal annealing program is: 125 °C, 40 min; 155 °C, 10 min. All other operations are the same.

[0065] The photoelectric performance of the 1.53 eV bandgap inverse perovskite solar cell prepared in this comparative example was tested, and the detailed test results are shown in Table 1. The effective test area was 0.058 cm². 2Under these conditions, its photoelectric conversion efficiency is 24.99%, and its short-circuit current density is 26.39 mA / cm². 2 The open-circuit voltage reaches 1.182 V, and the fill factor is 0.8011. Comparative Example 6

[0066] This comparative example relates to the fabrication of an inverted perovskite solar cell with a bandgap of 1.53 eV. The only difference from Example 1 is that it includes only two annealing processes. The thermal annealing program is: 55 °C for 5 min; 155 °C for 50 min. All other operations are the same.

[0067] The photoelectric performance of the 1.53 eV bandgap inverse perovskite solar cell prepared in this comparative example was tested, and the detailed test results are shown in Table 1. The effective test area was 0.058 cm². 2 Under these conditions, its photoelectric conversion efficiency is 25.88%, and its short-circuit current density is 26.38 mA / cm². 2 The open-circuit voltage reaches 1.190 V, and the fill factor is 0.8245. Comparative Example 7

[0068] This comparative example relates to the fabrication of an inverted perovskite solar cell with a bandgap of 1.53 eV. The only difference from Example 1 is that it includes only two annealing processes. The thermal annealing program is: 55 °C for 5 min; 125 °C for 50 min. All other operations are the same.

[0069] The photoelectric performance of the 1.53 eV bandgap inverse perovskite solar cell prepared in this comparative example was tested, and the detailed test results are shown in Table 1. The effective test area was 0.058 cm². 2 Under these conditions, its photoelectric conversion efficiency is 25.66%, and its short-circuit current density is 26.35 mA / cm². 2 The open-circuit voltage reaches 1.188 V, and the fill factor is 0.8198. Comparative Example 8

[0070] This comparative example relates to the preparation of an inverted perovskite solar cell with a bandgap of 1.53 eV. The only difference from Example 1 is that the content of MSM in the precursor solution is increased from 0.3 M to 0.6 M, while the rest of the operations are the same.

[0071] The photoelectric performance of the 1.53 eV bandgap inverse perovskite solar cell prepared in this comparative example was tested, and the detailed test results are shown in Table 1. The effective test area was 0.058 cm². 2 Under these conditions, its photoelectric conversion efficiency is 25.65%, and its short-circuit current density is 26.41 mA / cm². 2The open-circuit voltage reaches 1.184 V, and the fill factor is 0.8202. Comparative Example 9

[0072] This comparative example relates to the preparation of an inverted perovskite solar cell with a bandgap of 1.68 eV. The only difference from Example 5 is that NHS was not added to the precursor solution, while all other operations are the same.

[0073] The photoelectric conversion efficiency, short-circuit current density, open-circuit voltage, and fill factor of the 1.68 eV bandgap inverted perovskite solar cell prepared in this comparative example were tested. The test results are shown in Table 1: the area is 0.058 cm². 2 The perovskite solar cell exhibits a photoelectric conversion efficiency of 22.26% and a short-circuit current density of 21.99 mA / cm². 2 The open-circuit voltage is 1.231 V, and the fill factor is 0.8223.

[0074] The photoelectric performance test data of the perovskite solar cells prepared in the above embodiments and comparative examples are shown in Table 1 below: Table 1

[0075] As shown in Table 1, the perovskite solar cells with different structures, band gaps, and effective areas prepared in Examples 1-6 all exhibited excellent photoelectric conversion efficiency. This also demonstrates that the high-quality perovskite thin films prepared by the present invention through the introduction of specific additives and a synergistic hierarchical crystallization annealing process have excellent device structural versatility. Compared with solar cells prepared by traditional processes (Comparative Example 1), the solar cells with the same structure, band gap, and effective area prepared in Examples 1-4 all showed effective improvements in photoelectric conversion efficiency, open-circuit voltage, and fill factor.

[0076] As shown in Examples 1 and 2 and Comparative Examples 2-4, the type and content of additives affect the performance of the constructed devices. Using additives with excessively low or high temperatures, or those with poor solubility in perovskite, not only fails to effectively improve the photoelectric performance of the devices but may even degrade it. For example, the photoelectric conversion efficiency of solar cells prepared with added DMSO or sulfone (Comparative Examples 2 and 3) is lower than that of Comparative Example 1. Furthermore, as shown in Comparative Example 8, if too much MSM is added, the photoelectric performance of the prepared devices will actually decrease.

[0077] As can be seen from Example 1 and Comparative Examples 5-7, under the condition of adding the above-mentioned specific additives, any step of the three-step annealing process is indispensable; otherwise, the photoelectric performance of the prepared solar cell will not only be significantly reduced compared with Example 1, but may even be inferior to Comparative Example 1.

[0078] In summary, the three-step annealing process and the characteristics of the additives, such as melting point window and concentration, are indispensable. Through the synergistic effect of the specific additives and the progressive annealing process of "low-temperature shaping - medium-temperature liquid phase recrystallization - high-temperature purification", the crystallinity, orientation and compactness of the perovskite film are significantly improved. At the same time, the problems of carrier transport damage and stability reduction caused by the residue of traditional high-melting-point additives are effectively avoided. This provides a novel and controllable material preparation route for the preparation of high-efficiency and high-stability perovskite solar cells.

[0079] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A method for preparing a perovskite thin film, characterized in that, Includes the following steps: S1. Prepare perovskite precursor solution; The perovskite precursor solution contains an additive comprising sulfone and / or succinimide groups, the additive having a melting point of [missing information]. T m Meets 60℃≤ T m The temperature is ≤110 ℃, and the solubility of the additive in perovskite in the molten state at 110-130 ℃ is not less than 50 mg / g; The concentration of the additive in the perovskite precursor solution is 0.005 M-0.4 M; S2. The perovskite precursor solution is applied to the substrate surface to form a wet film, and then dried to obtain an intermediate film. S3. Perform multi-step annealing on the intermediate film to obtain the perovskite thin film; The multi-step annealing process includes sequentially performing a first annealing process, a second annealing process, and a third annealing process, wherein: The temperature of the first annealing treatment is 45 ℃-65 ℃, which is lower than the melting point of the additive. T m The time is 5-10 minutes; The temperature of the second annealing treatment is ( T m +10)℃-( T m +20℃, for 5-60 minutes; The third annealing treatment is performed at a temperature of 135 ℃-160 ℃ for a time of 5-45 min.

2. The preparation method according to claim 1, characterized in that, In step S1, the additive is selected from one or more of dimethyl sulfone, diethyl sulfone, N-methylsuccinimide, and N-hydroxysuccinimide; And / or, the concentration of the additive in the perovskite precursor solution is 0.01 M-0.3 M.

3. The preparation method according to claim 1, characterized in that, The perovskite film is a lead halide perovskite film with the chemical formula APbX3, wherein A is selected from one or more of formamidinium, methylamine and cesium, and X is a halogen.

4. The preparation method according to claim 3, characterized in that, In step S1, the molar ratio of lead ions to additives in the perovskite precursor solution is (3.75-300):

1.

5. The preparation method according to claim 1, characterized in that, In step S1, the perovskite precursor salt and additives are dissolved in a solvent to obtain a clear perovskite precursor solution. The perovskite precursor salt includes at least two of the following: formamidinium hydroiodate, lead iodide, methylamine hydrobromide, cesium iodide, lead bromide, lead chloride, and methylamine hydrochloride. The solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, and γ-valerolactone.

6. The preparation method according to claim 1, characterized in that, In step S2, the application method is spin coating, scraping coating, printing, or inkjet printing.

7. The preparation method according to claim 1, characterized in that, In step S2, the drying process specifically involves placing the substrate with the wet film on a cold plate for cooling, and then obtaining an intermediate film through vacuum flash evaporation. The temperature of the cold plate is -20 ℃ to 0 ℃, and the cooling time is 20-40 s; The vacuum degree of the vacuum flash evaporation is 0.1-20 Pa, and the time is 40-60 s.

8. A perovskite thin film, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. A perovskite solar cell device, characterized in that, It includes the perovskite thin film as described in claim 8.

10. The perovskite solar cell device according to claim 9, characterized in that, The perovskite solar cell device is a pin-type perovskite solar cell device or a nip-type perovskite solar cell device.

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