Preparation method of perovskite thin film and trans-perovskite solar cell

Abstract

The invention belongs to the technical field of photovoltaic cells, and particularly relates to a preparation method of a perovskite thin film and a trans-perovskite solar cell, a perovskite precursor solution is prepared based on CsI, FAI, MAI, MACL and PbI2, an additive tetrafluorosuccinic anhydride is added into the perovskite precursor solution, and the perovskite thin film is prepared through annealing. In the growth process of the film, the tetrafluorosuccinic anhydride has a C = O group and can be coordinated with Pb < 2 + > in the perovskite precursor solution, so that the non-coordination defect of the Pb < 2 + > is reduced, the non-radiative recombination center is reduced, the defect density is reduced, the integrity of the film is improved, and the crystal quality of the perovskite film is improved. In conclusion, the problems that an existing perovskite thin film has a large number of defects, the quality of the thin film is low, and the performance of a perovskite solar cell is seriously restricted are effectively solved.

Description

Technical Field

[0001] The invention belongs to the technical field of photovoltaic cells, and in particular relates to a method for preparing a perovskite film and an inverse perovskite solar cell. Background Art

[0002] In recent years, the photovoltaic power generation industry has shown a rapid development trend, and the photoelectric conversion efficiency of photovoltaic devices based on solar cells has been continuously improved. Among them, perovskite solar cells, as a photovoltaic technology with great potential, have the advantages of adjustable band gap, high absorption coefficient, high spectral response, and long carrier diffusion distance, and have attracted widespread attention in the field of solar cells. At present, 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 factor that determines the performance of the cell. This layer must have the ability to efficiently absorb light energy and effectively separate and transmit the generated electrons and holes. However, the defects in the perovskite layer have become the key to its quality. These defects include cation defects, anion defects and other types, and are usually unavoidable during the formation of perovskite films. They will not only destroy the structural integrity of the perovskite layer, causing its crystallinity to decrease, but also form non-radiative recombination centers. Non-radiative recombination refers to the recombination of electrons and holes at defects without generating photons. This process will greatly reduce the number of photons that can be converted into electrical energy, thereby 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 preparation of high-efficiency perovskite solar cells. Summary of the invention

[0004] The purpose of the present invention is to propose a method for preparing a perovskite film and an inverted perovskite solar cell in view of the fact that there are a large number of defects in existing perovskite films, including lattice mismatch, dislocation and holes, which lead to low film quality and seriously restrict the performance of perovskite solar cells.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

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

[0007] Step 1: CsI:FAI, MAI, MACL and PbI 2 , premixed in a molar ratio of 0.1:0.85:0.05:0.15:1, and then dispersed by adding a solvent to obtain a perovskite precursor A solution;

[0008] Step 2, adding 0.5 mg to 1.5 mg of tetrafluorosuccinic anhydride as an additive to the perovskite precursor A solution to obtain a perovskite precursor B solution;

[0009] Step 3: Spin-coat the perovskite precursor B solution onto the substrate using a spin coating method, and obtain a perovskite film after annealing.

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

[0011] Further, the spin coating method of step 3 is:

[0012] The rotation speed of the spin coater is divided into two stages, the rotation speed of the first stage is 500-1000 rpm, and the spin coating time is 5-20 s; the rotation speed of the second stage is 5000-6000 rpm, and the spin coating time is 30-50 s; 0.1-0.2 mL of chlorobenzene anti-solvent is dripped onto the rotating substrate surface 5-15 s after the start of the second spin coating; after the second stage spin coating is completed, annealing is performed at a temperature range of 100-120° C. for 10-15 min.

[0013] A perovskite film is prepared by the above-mentioned preparation method of adding tetrafluorosuccinic anhydride molecules to passivate the perovskite film.

[0014] An inverse perovskite solar cell comprises the above-mentioned perovskite film passivated by adding tetrafluorosuccinic anhydride molecules.

[0015] In the process of preparing perovskite films, specific additives are introduced to improve the nucleation and crystallization process of perovskite materials through the interaction between the additives and perovskites. These additives can be small molecules, ions or polymer materials, which can bind to defect sites in the perovskite layer to passivate these defects and reduce the frequency of non-radiative recombination. By precisely controlling the type and concentration of additives, the microstructure of the perovskite film can be adjusted to a certain extent, its electronic properties can be optimized, and its stability and photoelectric conversion efficiency can be improved. For example, some additives with specific functional groups can bind to the undercoordinated Pb in the perovskite. 2+ Mutual coordination allows the defects to be passivated and is also conducive to the formation of a more uniform and dense perovskite film.

[0016] Based on this, the present invention uses tetrafluorosuccinic anhydride molecules, which are used as vitamin A raw materials in the pharmaceutical field, as additives. By adding tetrafluorosuccinic anhydride molecules, the defects in the perovskite film are significantly reduced. During the film growth process, tetrafluorosuccinic anhydride has a C=O group, which will react with Pb in the perovskite precursor solution. 2+ Mutual coordination occurs, thereby reducing Pb 2+It can reduce non-coordination defects, reduce non-radiative recombination centers, lower defect density, improve film integrity, and help improve the crystalline quality of perovskite films.

[0017] In addition, the inverse perovskite solar cells prepared using perovskite films have significantly improved open circuit voltage, fill factor and photoelectric conversion efficiency. Among them, the increase in open circuit voltage is mainly due to the reduction in defect density, and the increase in fill factor is due to the improvement in film crystal quality. The present invention has the potential to promote the development of inverse perovskite solar cells. By optimizing the quality of the film, it is expected to further improve the stability and life of perovskite solar cells.

[0018] In summary, the present invention promotes grain growth by adding tetrafluorosuccinic anhydride, making the grain size larger and the grain boundaries fewer, thereby improving the crystallinity of the film, and effectively improving the existing perovskite film. The problem of a large number of defects, resulting in low film quality, and seriously restricting the performance of perovskite solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0020] Figure 2 Schematic diagram of the structure of an inverted perovskite solar cell prepared using the perovskite film obtained in Example 1;

[0021] Figure 3 This is a morphology of the perovskite film obtained in Comparative Example 1 under a scanning electron microscope (SEM);

[0022] Figure 4 This is a morphology of the perovskite film obtained in Example 1 under a scanning electron microscope (SEM);

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

[0024] Figure 6 The graphs are photoluminescence spectra (PL) of the perovskite films obtained in Example 1 and Comparative Example 1; wherein (a) is a standard PL graph, and (b) is a PL graph obtained after normalization treatment of the perovskite film with tetrafluorosuccinic anhydride additive;

[0025] Figure 7 The device JV curves of the inverted perovskite solar cells obtained in Example 1, Comparative Example 1 and Comparative Example 2 are shown. DETAILED DESCRIPTION

[0026] The technical solution of the present invention will be clearly and completely described below in combination with the embodiments and drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Unless otherwise defined, the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0028] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present 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 film, the process of which is as follows: Figure 1 As shown, the following steps are included:

[0031] Step A1: Prepare the perovskite precursor solution by weighing 19.5 mg of CsI, 219.3 mg of FAI, 23.8 mg of MAI, and 760.7 mg of PbI 2 , and 12.7 mg of MACL, and dissolved in 1 mL of a mixed solvent and stirred for 8 h to fully dissolve, thereby obtaining a perovskite precursor A solution. The mixed solvent consists of DMF and DMSO, and the volume ratio of DMF to DMSO is 4:1.

[0032] Step A2: Take 0.5 mg to 1.5 mg of tetrafluorosuccinic anhydride and add it to the perovskite precursor solution A to fully dissolve it, thereby obtaining a mixed additive precursor B solution.

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

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

[0035] Step B1: Cleaning the glass substrate:

[0036] In this embodiment, ITO glass is selected as the substrate; acetone and anhydrous ethanol are used for ultrasonic cleaning, respectively, each cleaning time is 20 minutes, the washed substrate is blown dry with a nitrogen gun and stored in a dry environment, and treated with a UV-ozone cleaning device for 20 minutes before use.

[0037] Step B2: Preparing 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)butyl)phosphonic acid (4PACz) is used as the hole transport layer, and 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) and place on an oscillating table until completely dissolved. Then, use an ultrasonic cleaning device for 15 minutes before use to make the NiO particles evenly dispersed to prepare 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 on the ITO substrate at a spin coating speed of 4000 rpm for 30 s, and then anneal on a hot stage at 100°C for 10 min. Then, spin coat the 4PACz solution on the NiO surface using a spin coater at a spin coating speed of 3000 rpm for 30 s, and then anneal on a hot stage at 100°C for 10 min to obtain a hole transport layer.

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

[0043] Step B4: Preparation of electron transport layer:

[0044] In this embodiment, LiF+C 60 The composite structure of +BCP is used as an electron transport layer, and the preparation method is as follows: 1 nm of LiF, 10 nm of C 60 and 15nm BCP.

[0045] Step B5: Preparation of metal electrodes:

[0046] In this embodiment, silver is used as the metal electrode. The preparation method is: 120 nm of silver is deposited on the surface of the electron transport layer by vacuum thermal evaporation through a mask, and then the following is obtained: Figure 2 The complete inverse perovskite solar cell shown.

[0047] Comparative Example 1

[0048] The perovskite film and the inverse perovskite solar cell prepared in this comparative example are different from those in Example 1 in that the process of preparing the additive solution in step A2 is not included, and the perovskite precursor solution obtained in step A1 is directly spin-coated on the substrate; the other steps are exactly the same. Then, a perovskite film and an inverse perovskite solar cell based on the perovskite film are obtained.

[0049] The above-mentioned Example 1 and Comparative Example 1 are analyzed and tested below:

[0050] The perovskite films obtained in Example 1 and Comparative Example 1 were analyzed by SEM. Figure 3 Corresponding to the perovskite film obtained in Example 1, Figure 4 The perovskite film obtained in Example 1 is compared with that in Example 1. Compared with Example 1, after adding tetrafluorosuccinic anhydride, not only the grain size of Example 1 is significantly increased, but also the morphology is more compact. In addition, compared with Example 1, the white byproduct PbI 2 The number of PbI 2 The reaction becomes perovskite, which means it can improve the crystal quality.

[0051] XRD analysis was performed on the perovskite films obtained in Example 1 and Comparative Example 1, respectively. Figure 5 It can be seen that the XRD spectrum represents PbI 2 The characteristic peak at 12.7° of the perovskite film decreased significantly with the addition of tetrafluorosuccinic anhydride, indicating that the PbI 2 The content of PbI in the perovskite film is reduced, indicating that the addition of tetrafluorosuccinic anhydride can effectively regulate the content of PbI 2 At the same time, the characteristic peak position of Example 1 and Comparative Example 1 at the 14.2° position representing the perovskite (100) crystal plane is the same, and no shift phenomenon occurs, indicating that the addition of tetrafluorosuccinic anhydride film has no effect on the composition and structure of the perovskite, but only exists at the grain boundaries and surfaces.

[0052] The PL spectrum analysis of the perovskite films obtained in Example 1 and Comparative Example 1 was performed 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 the non-radiative recombination in the perovskite film and reduces the defect density; in addition, Figure 6 As shown in (b), after normalizing the PL spectrum of the perovskite film of Comparative Example 2, it is found that the PL peak position has a small blue shift compared with the film of Comparative Example 1. This is because the C=O group in tetrafluorosuccinic anhydride binds to the Pb on the perovskite film. 2+ interaction, reducing the density of trap states and limiting charge recombination.

[0053] Photovoltaic tests were performed on the inverted perovskite solar cells obtained in Example 1 and Comparative Example 1, respectively, and the effective active area was 0.053 cm 2 The test conditions are standard simulated sunlight AM1.5 and temperature 25℃. The obtained JV curve is shown in the figure below. Figure 7 As shown in Table 1, the photovoltaic parameters show that the open circuit voltage of the inverted perovskite solar cell obtained in Example 1 is 1.161 V, and the short circuit current is 24.39 mA / cm 2 , the filling factor is 76.39%, and the energy conversion efficiency is 21.62%. Compared with Comparative Example 1, the open circuit voltage and the filling factor of Example 1 are greatly improved, and the photoelectric conversion efficiency is thus improved by nearly 13.9% compared with Comparative Example 1, which indicates that the addition of tetrafluorosuccinic anhydride in the process of preparing the perovskite film significantly optimizes the photovoltaic performance of the inverted solar cell device.

[0054] Table 1 Comparison of performance of perovskite solar cells between Example 1 and Comparative Example 1

[0055]

[0056]

[0057] The above embodiments are intended to provide a better understanding of the present invention, but are not limited to the optimal implementation mode and do not constitute a limitation on the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the present invention with the features of other prior arts shall be within the protection scope of the present invention.

Claims

1. A method for preparing a perovskite film, characterized in that: The following steps are involved: Step 1, pre-mix CsI:FAI, MAI, MACL and PbI2 according to a molar ratio of 0.1:0.85:0.05:0.15:1, add a solvent for dispersion, and prepare a perovskite precursor A solution; Step 2, adding 0.5 mg to 1.5 mg of tetrafluorosuccinic anhydride as an additive to the perovskite precursor A solution to obtain a perovskite precursor B solution; Step 3: Spin-coat the perovskite precursor B solution onto the substrate using a spin coating method, and obtain a perovskite film after annealing.

2. The method for preparing a perovskite thin film according to claim 1, characterized in that: The solvent is a mixed solvent of DMF and DMSO in a volume ratio of 4:

1.

3. The method for preparing a perovskite thin film according to claim 1, characterized in that: The spin coating method of step 3 is: The rotation speed of the spin coater is divided into two stages, the rotation speed of the first stage is 500-1000 rpm, and the spin coating time is 5-20 s; the rotation speed of the second stage is 5000-6000 rpm, and the spin coating time is 30-50 s; 0.1-0.2 mL of chlorobenzene anti-solvent is dripped onto the rotating substrate surface 5-15 s after the start of the second spin coating; after the second stage spin coating is completed, annealing is performed at a temperature range of 100-120° C. for 10-15 min.

4. A perovskite film, characterized in that: The perovskite film is prepared by the method for preparing the perovskite film according to any one of claims 1 to 3.

5. An inverted perovskite solar cell, characterized in that: Comprising the perovskite film as described in claim 4.

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