A method for preparing a perovskite thin film and an inverted perovskite solar cell

Abstract

This invention belongs to the field of photovoltaic cell technology, specifically relating to a method for preparing a perovskite thin film and an inverted perovskite solar cell. First, a perovskite precursor solution is prepared based on CsI, FAI, MAI, MACL, and PbI2. Then, tetrafluorosuccinic anhydride is added as an additive to the perovskite precursor solution, followed by annealing to obtain the perovskite thin film. During the film growth process, because tetrafluorosuccinic anhydride has C=O groups, it reacts with Pb in the perovskite precursor solution. 2+ Mutual coordination occurs, thereby reducing Pb 2+ The invention addresses the non-coordination defects, reduces non-radiative recombination centers, lowers defect density, improves film integrity, and contributes to enhancing the crystallinity of perovskite films. In summary, this invention effectively improves upon the problems of existing perovskite films, which suffer from numerous defects, resulting in low film quality and severely limiting the performance of perovskite solar cells.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic cell technology, specifically relating to a method for preparing a perovskite thin film and an inverted perovskite solar cell. Background Technology

[0002] In recent years, the photovoltaic power generation industry has shown rapid development, and the photoelectric conversion efficiency of photovoltaic devices based on solar cells has been continuously improving. Among them, perovskite solar cells, as a highly promising photovoltaic technology, have attracted widespread attention in the field of solar cells due to their advantages such as tunable bandgap, high absorption coefficient, high spectral response, and long carrier diffusion distance. Currently, the photoelectric conversion efficiency of single-junction perovskite solar cells has reached 26.7%.

[0003] In the structure of perovskite solar cells, the perovskite layer is undoubtedly the key element determining the performance of the cell. This layer must not only have the ability to efficiently absorb light energy, but also effectively separate and transport the generated electrons and holes. However, defects in the perovskite layer have become a critical factor affecting its quality. These defects include various types such as cation defects and anion defects, and are usually unavoidable during the formation of perovskite films. They not only disrupt the structural integrity of the perovskite layer, leading to a decrease in its crystallinity, but also form nonradiative recombination centers. Nonradiative recombination refers to the recombination of electrons and holes at defects without producing photons. This process significantly reduces the number of photons that can be converted into electrical energy, thus significantly reducing the photoelectric conversion efficiency of perovskite solar cells. Therefore, how to effectively passivate these defects to obtain high-quality, high-crystallinity perovskite films has become the core issue in the fabrication of high-efficiency perovskite solar cells. Summary of the Invention

[0004] The purpose of this invention is to address the numerous defects in existing perovskite thin films, including lattice mismatch, dislocations, and voids, which lead to low film quality and severely restrict the performance of perovskite solar cells. This invention proposes a method for preparing perovskite thin films and an inverted perovskite solar cell.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing a perovskite thin film includes the following steps:

[0007] Step 1: Premix CsI:FAI, MAI, MACL and PbI2 in a molar ratio of 0.1:0.85:0.05:0.15:1, then add solvent to disperse them to obtain perovskite precursor A solution;

[0008] Step 2: Add 0.5 mg to 1.5 mg of tetrafluorosuccinic anhydride to the perovskite precursor A solution to obtain the perovskite precursor B solution.

[0009] Step 3: Spin-coating the perovskite precursor B solution onto the substrate using a spin-coating method, followed by annealing to obtain a perovskite thin film.

[0010] Furthermore, the solvent is a mixed solvent composed of DMF and DMSO at a volume ratio of 4:1.

[0011] Furthermore, the spin coating method in step 3 is as follows:

[0012] The spin coater operates in two stages. The first stage operates at 500–1000 rpm for 5–20 seconds. The second stage operates at 5000–6000 rpm for 30–50 seconds. 5–15 seconds after the start of the second spin coat, 0.1–0.2 mL of chlorobenzene anti-solvent is dropped onto the rotating substrate surface. After the second spin coat is completed, the substrate is annealed at 100–120°C for 10–15 minutes.

[0013] A perovskite thin film is prepared by the above-described method of passivating perovskite thin films with added tetrafluorosuccinic anhydride molecules.

[0014] An inverted perovskite solar cell having the above-mentioned perovskite thin film passivated by the addition of tetrafluorosuccinic anhydride molecules.

[0015] Introducing specific additives during the preparation of perovskite thin films can improve the nucleation and crystallization processes of perovskite materials through interactions between the additives and the perovskite. These additives can be small molecules, ions, or polymers, capable of binding to defect sites in the perovskite layer, thereby passivating these defects and reducing the frequency of nonradiative recombination. By precisely controlling the type and concentration of additives, the microstructure of the perovskite thin film can be tuned to a certain extent, optimizing its electronic properties and improving its stability and photoelectric conversion efficiency. For example, certain additives with specific functional groups can bind to undercoordinated Pb in the perovskite. 2+ Mutual coordination allows defects to be passivated and also facilitates the formation of more uniform and dense perovskite films.

[0016] Based on this, the present invention uses tetrafluorosuccinic anhydride molecules, which are used as a raw material for vitamin A in the pharmaceutical field, as an additive. By adding tetrafluorosuccinic anhydride molecules, defects in perovskite films are significantly reduced. During film growth, because tetrafluorosuccinic anhydride has C=O groups, it reacts with Pb in the perovskite precursor solution. 2+ Mutual coordination occurs, thereby reducing Pb 2+The non-coordination defects reduce non-radiative recombination centers, lower defect density, improve film integrity, and contribute to improving the crystallinity quality of perovskite films.

[0017] Furthermore, inverted perovskite solar cells fabricated using perovskite thin films exhibit significant improvements in open-circuit voltage, fill factor, and photoelectric conversion efficiency. The increase in open-circuit voltage is primarily due to a reduction in defect density, while the improvement in fill factor is attributed to enhanced film crystallinity. This invention has the potential to promote the development of inverted perovskite solar cells. By optimizing film quality, it is expected to further improve the stability and lifetime of perovskite solar cells.

[0018] In summary, this invention promotes grain growth by adding tetrafluorosuccinic anhydride, resulting in larger grain size and fewer grain boundaries, thereby improving the crystallinity of the thin film. This effectively addresses the problems of existing perovskite thin films having numerous defects, leading to low film quality and severely restricting the performance of perovskite solar cells. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the preparation process of the perovskite thin film in Example 1;

[0020] Figure 2 This is a schematic diagram of the structure of an inverted perovskite solar cell prepared using the perovskite thin film obtained in Example 1;

[0021] Figure 3 The image shows the morphology of the perovskite film obtained in Comparative Example 1 under a scanning electron microscope (SEM).

[0022] Figure 4 The image shows the morphology of the perovskite film obtained in Example 1 under a scanning electron microscope (SEM).

[0023] Figure 5 Normalized X-ray diffraction (XRD) patterns of the perovskite films obtained in Example 1 and Comparative Example 1;

[0024] Figure 6 The photoluminescence (PL) spectra of the perovskite films obtained in Example 1 and Comparative Example 1 are shown; where (a) is the standard PL spectra and (b) is the PL spectra obtained after normalization of the perovskite films with added tetrafluorosuccinic anhydride additive.

[0025] Figure 7 The JV curves of the inverted perovskite solar cells obtained in Example 1 and Comparative Examples 1 and 2 are shown. Detailed Implementation

[0026] The technical solution of the present invention will now be clearly and completely described in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0028] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0029] Example 1

[0030] This embodiment provides a method for preparing a perovskite thin film, the process of which is as follows: Figure 1 As shown, it includes the following steps:

[0031] Step A1: Prepare the perovskite precursor solution. Weigh 19.5 mg of CsI, 219.3 mg of FAI, 23.8 mg of MAI, 760.7 mg of PbI2, and 12.7 mg of MACL, and dissolve them in 1 mL of a mixed solvent. Stir for 8 hours to ensure complete dissolution, thus obtaining perovskite precursor solution A. The mixed solvent consists of DMF and DMSO, with a volume ratio of DMF to DMSO of 4:1.

[0032] Step A2: Add 0.5 mg to 1.5 mg of tetrafluorosuccinic anhydride to perovskite precursor solution A and dissolve it completely to obtain mixed additive precursor solution B.

[0033] Step A3: Spin-coat the mixed additive precursor solution onto an indium tin oxide (ITO) glass substrate. The spin-coating is divided into two stages. The first stage has a rotation speed of 1000 rpm and a duration of 10 s. The second stage has a rotation speed of 6000 rpm and a duration of 30 s. At the 25th second of the second stage, 0.135 mL of chlorobenzene antisolvent is dropped onto the rotating glass substrate surface. After spin-coating is completed, place it on a hot stage and anneal at 120 °C for 10 min to obtain a perovskite thin film.

[0034] This embodiment also provides an inverted perovskite solar cell, with the structure as follows: Figure 2As shown, the structure includes, from bottom to top, a glass substrate, indium tin oxide, a hole transport layer, a perovskite layer, an electron transport layer, and a metal electrode layer; wherein the perovskite layer is a perovskite thin film obtained according to steps A1-A3. The fabrication method of the inverted perovskite solar cell in this embodiment is as follows:

[0035] Step B1: Clean the glass substrate:

[0036] In this embodiment, ITO glass was used as the substrate. The substrate was ultrasonically cleaned with acetone and anhydrous ethanol for 20 minutes each. The cleaned substrate was dried with a nitrogen gun and stored in a dry environment. Before use, it was treated with a UV-ozone cleaning device for 20 minutes.

[0037] Step B2: Fabricate a hole transport layer on a glass substrate:

[0038] In this embodiment, a composite structure of nickel oxide (NiO) and (4-(3,6-dimethyl-9H-carbazole-9-yl)butylphosphonic acid (4PACz) is selected as the hole transport layer. The preparation steps are as follows:

[0039] Step B2.1: Weigh 15 mg of NiO and add 0.75 ml of deionized water and 0.25 ml of isopropanol solution (Alfaesar). Place the solution on a shaking table until completely dissolved, and treat it with an ultrasonic cleaner for 15 min before use to ensure that the NiO particles are evenly dispersed, thus preparing a NiO solution.

[0040] Step B2.2: Weigh a certain amount of 4PACz and dissolve it in anhydrous ethanol to prepare a 4PACz solution with a concentration of 1 mg / mL;

[0041] Step B2.3: Spin-coat the NiO solution obtained in step B2.1 onto the ITO substrate at a spin coating speed of 4000 rpm for 30 s. Then anneal at 100 °C for 10 min on a hot plate. Next, spin-coat the 4PACz solution onto the NiO surface at a spin coating speed of 3000 rpm for 30 s. Then anneal at 100 °C for 10 min on a hot plate to obtain the hole transport layer.

[0042] Step B3: Following steps A1 to A4 above, prepare a perovskite layer on the hole transport layer;

[0043] Step B4: Fabrication of the electron transport layer:

[0044] This embodiment uses LiF+C 60 The composite structure of +BCP serves as an electron transport layer, and its preparation method is as follows: 1 nm of LiF and 10 nm of C are sequentially deposited on the surface of the perovskite layer obtained in step B3 by vacuum thermal evaporation. 60 And 15nm BCP.

[0045] Step B5: Fabrication of the metal electrode:

[0046] In this embodiment, silver is selected as the metal electrode. The preparation method is as follows: 120 nm of silver is deposited on the surface of the electron transport layer using vacuum thermal evaporation through a mask, thereby obtaining the desired result. Figure 2 The complete inverted perovskite solar cell is shown.

[0047] Comparative Example 1

[0048] The perovskite thin film and inverted perovskite solar cell prepared in this comparative example differ from those in Example 1 only in that the additive solution preparation process in step A2 is omitted, and the perovskite precursor solution obtained in step A1 is directly spin-coated onto the substrate; all other steps are exactly the same. This results in a perovskite thin film and an inverted perovskite solar cell based on this perovskite thin film.

[0049] The following analysis and testing are conducted on Example 1 and Comparative Example 1 as described above:

[0050] SEM analysis was performed on the perovskite films obtained in Example 1 and Comparative Example 1, respectively. Figure 3 For the perovskite thin film obtained in response ratio 1, Figure 4 Compared to the perovskite film obtained in Comparative Example 1, the addition of tetrafluorosuccinic anhydride in Example 1 not only significantly increased the grain size but also resulted in a more compact morphology. Furthermore, compared to Comparative Example 1, the amount of the white byproduct PbI2 on the surface of the film in Example 1 was significantly reduced. This indicates that the introduction of tetrafluorosuccinic anhydride can regulate the reaction of PbI2 to form perovskite, suggesting that it can improve the crystallinity.

[0051] XRD analysis was performed on the perovskite films obtained in Example 1 and Comparative Example 1, respectively. Figure 5 As can be seen from the XRD pattern, the characteristic peak representing PbI2 at the 12.7° position significantly decreases with the addition of tetrafluorosuccinic anhydride, indicating a reduction in the PbI2 content in the perovskite film. This demonstrates that adding tetrafluorosuccinic anhydride can effectively regulate the lead iodide (PbI2) content in the perovskite film. Meanwhile, the characteristic peak at the 14.2° position representing the perovskite (100) crystal plane is the same in Example 1 and Comparative Example 1, showing no shift. This indicates that the addition of tetrafluorosuccinic anhydride did not affect the composition and structure of the perovskite film, but only existed at the grain boundaries and surface.

[0052] PL spectroscopy analysis was performed on the perovskite films obtained in Example 1 and Comparative Example 1, respectively. Figure 6 (a) and Figure 6(b) It can be seen that the characteristic peak intensity of the perovskite film obtained in Example 1 at 750–850 nm is much higher than that in Comparative Example 1, indicating that the addition of tetrafluorosuccinic anhydride reduces non-radiative recombination in the perovskite film and reduces the defect density; in addition, as Figure 6 As shown in (b), after normalizing the PL spectrum of the perovskite film in Comparative Example 2, a slight blue shift was observed in the PL peak position compared to the film in Comparative Example 1. This is because the C=O groups in tetrafluorosuccinic anhydride react with the Pb on the perovskite film. 2+ Interactions reduce the density of trapped states and limit charge recombination.

[0053] Photovoltaic tests were conducted on the inverted perovskite solar cells obtained in Example 1 and Comparative Example 1, respectively, and the effective active area was 0.053 cm². 2 The test conditions were standard simulated sunlight AM1.5 and a temperature of 25℃. The resulting JV curve is shown below. Figure 7 As shown in Table 1, the photovoltaic parameters are as follows: The open-circuit voltage of the inverted perovskite solar cell obtained in Example 1 is 1.161V, and the short-circuit current is 24.39mA / cm². 2 The fill factor was 76.39% and the power conversion efficiency was 21.62%. Compared with Comparative Example 1, the open-circuit voltage and fill factor of Example 1 were greatly improved, and the photoelectric conversion efficiency was improved by nearly 13.9% compared with Comparative Example 1. This shows that the addition of tetrafluorosuccinic anhydride during the preparation of perovskite thin film significantly optimized the photovoltaic performance of the inverted solar cell device.

[0054] Table 1. Performance comparison of perovskite solar cells in Example 1 and Comparative Example 1

[0055]

[0056]

[0057] The above embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, is within the scope of protection of the present invention.

Claims

1. A method for preparing a perovskite thin film, characterized in that, Includes the following steps: Step 1: CsI:FAI, MAI, MACL and PbI2 are premixed in a molar ratio of 0.1:0.85:0.05:0.15:1, and then dispersed in a solvent to obtain perovskite precursor A solution; the solvent is a mixed solvent of DMF and DMSO in a volume ratio of 4:

1. Step 2: Add 0.5 mg to 1.5 mg of tetrafluorosuccinic anhydride to the perovskite precursor A solution to obtain perovskite precursor B solution. Step 3: Spin-coating the perovskite precursor B solution onto the substrate using a spin-coating method, followed by annealing to obtain a perovskite thin film.

2. The method for preparing a perovskite thin film according to claim 1, characterized in that, The spin coating method in step 3 is as follows: The spin coater operates in two stages. The first stage operates at 500-1000 rpm for 5-20 seconds. The second stage operates at 5000-6000 rpm for 30-50 seconds. 5-15 seconds after the start of the second spin coat, 0.1-0.2 mL of chlorobenzene anti-solvent is dropped onto the rotating substrate surface. After the second spin coat is completed, the substrate is annealed at 100-120°C for 10-15 minutes.

3. A perovskite thin film, characterized in that, The perovskite thin film was prepared using the method described in claim 1 or 2.

4. A reverse perovskite solar cell, characterized in that, Includes the perovskite thin film as described in claim 3.

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