A lead-tin blended perovskite film and its preparation method and application

Abstract

The present invention discloses a lead-tin blended perovskite film and its preparation method and application, belonging to the field of solar cell technology. The lead-tin blended perovskite film is prepared by adding a strong polar passivating agent to a lead-tin blended perovskite precursor solution. The present invention utilizes a strong polar molecule to perform bulk passivation on the lead-tin blended perovskite, which can more effectively passivate the A-site and B-site defects in the bulk and surface of the thick lead-tin blended perovskite, thereby increasing the diffusion length of carriers. While increasing the thickness of the light-absorbing layer to absorb more sunlight, it ensures that the photogenerated carriers are still effectively transmitted to the transmission layer at both ends, thereby increasing the short-circuit current density of single-junction and stacked perovskite cells and improving the efficiency of the cell's photoelectric conversion.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cells, and in particular relates to a lead-tin blended perovskite film and a preparation method and application thereof. Background Art

[0002] Perovskite solar cells (PSCs) are third-generation solar cells that utilize organic-inorganic hybrid metal halide semiconductors (PMSs) as light-absorbing materials. These hybrid PSCs have attracted significant international attention due to their low cost, ease of fabrication, and excellent photoelectric conversion performance. They are rapidly developing, with conversion efficiency increasing from 3.8% in 2009 to 25.5% in 2020. Perovskite materials are considered the next generation of low-cost, light-absorbing materials for solar cells.

[0003] To achieve higher photoelectric conversion efficiency for perovskite cells, perovskite-based tandem cells are the most effective approach to breaking through this efficiency barrier. In perovskite / perovskite tandem solar cells, a wide-bandgap perovskite is used as the top cell to absorb short-wavelength sunlight, while a narrow-bandgap perovskite is used as the bottom cell to absorb long-wavelength sunlight. This improves the utilization of the solar spectrum and reduces thermal relaxation losses of carriers in single-junction cells, thereby increasing photoelectric conversion efficiency. However, the efficiency of perovskite / perovskite solar cells is currently severely limited by narrow-bandgap perovskite solar cells. This is because narrow-bandgap perovskite solar cells need to absorb long-wavelength sunlight, which has a long penetration depth and requires a thick perovskite absorber layer for sufficient absorption. However, while thick absorbers can fully absorb sunlight, the short lifetime of photogenerated carriers results in insufficient diffusion length, preventing photogenerated carriers from effectively traversing the thick absorber layer to reach the transport layers at both ends. Consequently, devices with thick absorbers that fully utilize sunlight actually perform worse than those with thinner absorbers. Summary of the Invention

[0004] To address the problems of poor quality, short carrier lifetime, and insufficient diffusion length of lead-tin blended perovskite films, the present invention provides a lead-tin blended perovskite film obtained by bulk passivation using strongly polar molecules. By using strongly polar molecules to bulk-passivate the lead-tin blended perovskite, both the bulk and surface A-site and B-site defects of the thick lead-tin blended perovskite can be more effectively passivated, thereby increasing the diffusion length of carriers. While increasing the thickness of the light-absorbing layer to absorb more sunlight, it ensures that photogenerated carriers are still effectively transmitted to the transmission layers at both ends, thereby increasing the short-circuit current density of single-junction and stacked perovskite cells and improving the efficiency of the cell's photoelectric conversion.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0006] A lead-tin blended perovskite film, wherein the lead-tin blended perovskite film is prepared by adding a strong polar passivating agent to a lead-tin blended perovskite precursor solution;

[0007] The strong polar passivating agent is one or more of 4-trifluoro-anilinium salt CF3-PAX, 4-trifluoro-benzylamine salt CF3-PMAX, 4-trifluoro-benzylamine salt CF3-PEAX, 4-fluoroanilinium salt F-PAX, 4-fluorobenzylamine salt F-PMAX or 4-fluorobenzylamine salt F-PEAX, as shown in the following formula, wherein X is chlorine, bromine, iodine or fluorine;

[0008]

[0009] The lead-tin blended perovskite film is ABX3, where the A position is methylamine ion MA + or formamidinium ion FA + One or a mixture of two of the following: + and tin ions Sn 2+ Blended, and tin ions Sn 2+ The proportion of metal ions is 10%-90%, and the X position is iodide ion I - 、Br - and chloride ions Cl - One or a mixture of two or three.

[0010] Furthermore, the amount of the strong polar passivator is 0.01%-10% of the sum of the molar amounts of lead ions and tin ions in the lead-tin blended perovskite precursor.

[0011] Furthermore, the amount of the strong polar passivator is 0.1%-1% of the sum of the molar amounts of lead ions and tin ions in the lead-tin blended perovskite precursor.

[0012] The method for preparing the lead-tin blended perovskite thin film comprises the following steps:

[0013] Step 1: preparing a lead-tin blended perovskite precursor solution according to a conventional method;

[0014] Step 2, adding a strong polar passivating agent to the lead-tin blended perovskite precursor solution, stirring, filtering and waiting for use;

[0015] Step 3: Prepare a lead-tin blended perovskite film by spin coating, blade coating or spraying the solution obtained in step 2.

[0016] Application of the above-mentioned lead-tin blended perovskite film in the preparation of perovskite solar cells.

[0017] A perovskite solar cell comprises the above-mentioned lead-tin blended perovskite film.

[0018] Furthermore, the thickness of the lead-tin blended perovskite film is 200-2000 nm.

[0019] Furthermore, the thickness of the lead-tin blended perovskite film is 1000-1500 nm.

[0020] The present invention provides a method for preparing lead-tin blended perovskite thin films using a bulk passivation method with highly polar molecules. Compared to other types of passivation materials, highly polar molecules can increase the passivation coverage of perovskite A-site defects and enhance their adsorption on the defects. Compared to surface passivation, bulk passivation effectively passivates both surface defects and internal defects in the perovskite. Compared to the passivation method for two-dimensional perovskites generated using phenylethylamine (PEA) series, this passivation method effectively prevents the formation of two-dimensional perovskites, thus preventing their adverse effects on carrier transport in perovskite solar cells and increasing the short-circuit current density of the solar cells. This passivation method can more effectively passivate both the bulk and surface of thick lead-tin blended perovskites. While increasing the thickness of the light-absorbing layer to absorb more sunlight, it also ensures that photogenerated carriers are effectively transported to the transport layers at both ends, thereby increasing the short-circuit current density of single-junction and stacked perovskite cells and improving the photovoltaic efficiency of the cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the principle of passivating perovskite film with a strong polar passivator in the present invention.

[0022] Figure 2 This is a structural diagram of the lead-tin blended perovskite solar cell in Example 1.

[0023] Figure 3 These are the performance parameters of the lead-tin perovskite solar cell with different passivation materials at a thickness of 1200 nm in Example 1.

[0024] Figure 4 Comparison of XRD patterns of the highly polar passivating agent and other passivating molecules in Example 1.

[0025] Figure 5 The carrier lifetime comparison of the perovskite film with the strong polar passivator CF3-PA added and the perovskite film without the passivation molecule added in Example 1 is shown.

[0026] Figure 6 In Example 1, the light intensity is 100mW / cm 2 Current density-voltage curves of large-area lead-tin blend perovskite solar cells under different conditions.

[0027] Figure 7The JV curves, external quantum efficiency (EQE) and integrated current of the lead-tin blended narrow bandgap solar cell at different thicknesses in Example 1 are shown. DETAILED DESCRIPTION

[0028] At present, in perovskite solar cells, the thin lead-tin blend perovskite light-absorbing layer (thickness less than 1μm) cannot fully utilize the long-wavelength solar energy, which leads to low photocurrent. Although the absorption of sunlight can be increased by increasing the thickness of the light-absorbing layer, the diffusion length of the carriers is insufficient, resulting in the inability of the carriers to diffuse but on the transmission layers at both ends. This makes the short-circuit current density of the perovskite single junction and stacked cells low, and the photoelectric conversion efficiency is also low.

[0029] The present invention introduces a strong polar passivator into a lead-tin blended perovskite precursor solution. The strong polar passivator can interact with the A-site and B-site defects of the perovskite and firmly adsorb on the defects, thereby improving the coverage of defect passivation. The lead-tin blended perovskite with a thick light-absorbing layer is fully passivated from both the bulk and the surface, increasing the diffusion length of carriers, thereby increasing the short-circuit current of the solar cell and improving the photoelectric conversion efficiency of single-junction and stacked cells.

[0030] In the present invention, the lead-tin blended perovskite has an ABX3 structure. Wherein: the A position can be a cesium ion (Cs + ), methylamino (MA + ) and formamidinyl (FA + ) or any combination of two or three of them in any proportion; the B position is lead ion (Pb 2+ ) and tin ions (Sn 2+ ) blended, and Sn 2+ The ratio can be any ratio from 10 to 90%; the X position can be an iodide ion (I - ), bromide ion (Br - ) and chloride ions (Cl - ) or any combination of two or three in any proportion.

[0031] In the present invention, the strong polar passivator has one or more charges or charge groups in its molecules. The strong polar molecules interact with the defects and are firmly adsorbed on the defects to passivate the defects. The process is: - +E + -E - =D - —E + -E - and D + +E — E + =D + —E - -E + , where E+ -E - or E - -E + The strong polar passivating agent is one or more of 4-trifluoro-anilinium salt CF3-PAX, 4-trifluoro-benzylamine salt CF3-PMAX, 4-trifluoro-phenylethylamine salt CF3-PEAX, 4-fluoroanilinium salt F-PAX, 4-fluorobenzylamine salt F-PMAX, or 4-fluorophenylethylamine salt F-PEAX, wherein X can be chlorine, bromine, iodine, or fluorine.

[0032]

[0033] For example: CF3 - -PA + CF3 in - and PA + .

[0034] In a specific embodiment of the present invention, 4-trifluoromethylaniline hydrochloride CF3-PACl is selected as the strong polar passivating agent.

[0035] The structural formula of CF3-PACl in the perovskite precursor solution is as follows:

[0036]

[0037] In 4-trifluoromethylaniline hydrochloride (CF3-PACl), CF3 is a group with a negative electron cloud, PA(NH3 + ) is a group with a positive charge.

[0038] The principle of CF3-PACl passivation of perovskite film is as follows Figure 1 As shown in Figure 2, the highly polar molecules composed of CF3-PACl can be firmly adsorbed on the perovskite defects, increasing the passivation coverage. The amine groups on the CF3-PACl molecules can interact with the A-site or B-site defects of the perovskite to passivate the defects and improve the quality of the perovskite film.

[0039] In the present invention, the amount of CF3-PACl added is 0.01%-10% of the total molar amount of lead and tin ions in the lead-tin blended perovskite precursor. The inventors have found that when the addition amount is less than 0.1% mol, the passivation effect is not significant, resulting in insignificant improvements in open-circuit voltage, off-circuit current, and fill factor. Furthermore, the addition amount is preferably 0.1%-1%, and more preferably 0.3% mol.

[0040] Before preparing the lead-tin blend perovskite layer, a highly polar passivating agent is added to the lead-tin blend perovskite precursor solution and then stirred thoroughly to uniformly disperse the passivating agent molecules in the solution. This allows for simultaneous passivation of the perovskite bulk and surface interface during subsequent film preparation. The lead-tin blend perovskite layer can be prepared by applying the precursor solution to the precursor solution using any of the following processing methods: spin coating, blade coating, or spray coating. Anti-solvent extraction can also be performed during the spin coating, blade coating, or spraying process.

[0041] By applying the above-mentioned lead-tin blended perovskite layer as a light absorption layer to a perovskite solar cell, a regular structure perovskite solar cell and a reverse structure perovskite solar cell can be obtained. The thickness of the light absorption layer is 200-2000nm, preferably 1000-1500nm.

[0042] To further illustrate the present invention, the technical solutions provided by the present invention are described in detail below with reference to the following examples. However, it should be understood that these descriptions are intended only to further illustrate the features and advantages of the present invention and are not intended to limit the scope of the present invention. All raw materials in the present invention are not particularly limited in their sources and can be purchased commercially or prepared according to conventional methods known to those skilled in the art.

[0043] Example 1

[0044] Lead-tin blended perovskite layers with CF3-PACl, other passivation molecules (phenylethylamine chloride PEACl, aniline chloride PACl), and no CF3-PA (Control) were used to prepare solar cells, and the performance of related devices was investigated.

[0045] like Figure 2 As shown in FIG, the structure of the solar cell of this embodiment includes an indium tin oxide (ITO) conductive glass substrate 1, a polyethylene dioxythiophene (PEDOT:PSS) hole transport layer 2, a lead-tin mixed perovskite light absorption layer 3 containing a strong polar passivation molecule, and a fullerene (C 60 ) / 2,9-dimethyl-4,7-biphenyl-1,10-o-phenanthroline (BCP) electron transport layer 4 and metal copper Cu electrode 5.

[0046] The preparation method of the above solar cell is as follows:

[0047] (1) The ITO transparent conductive substrate was scrubbed with deionized water mixed with ITO cleaning solution, and then ultrasonicated with deionized water, acetone, and isopropyl alcohol for 30 minutes each to obtain a cleaned ITO transparent conductive substrate.

[0048] (2) Blow the cleaned ITO transparent conductive substrate clean with a N2 air gun and pre-treat it with UV ozone for 15-20 minutes.

[0049] (3) Prepare a 40-50 nm thick layer of PEDOT:PSS as a hole transport layer on an ITO transparent conductive substrate pretreated with UV ozone and anneal on a hot plate at 150°C for 20 min. Store the substrate with the transport layer in a glove box filled with an inert gas such as nitrogen or argon.

[0050] (4) Weigh MA by molar ratio in a glove box filled with inert gas such as nitrogen or argon. 0.3 FA 0.7 Pb 0.5 Sn 0.5 I3 perovskite, adding Pb 2+ 、Sn 2+ The molar sum of 0.3% of the strong polar passivator 4-trifluoro-phenylammonium chloride (CF3-PACl) and 5% molar ratio of stannous fluoride (SnF2) is recorded as CF3-PA, 0.2% of phenylethylammonium chloride (PEACl) and 5% molar ratio of stannous fluoride (SnF2) are recorded as PEA, 0.3% of phenylammonium chloride (PACl) and 5% molar ratio of stannous fluoride (SnF2) are recorded as PA, and the weighed drugs are dissolved in a mixed solution of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) with a volume ratio of DMF and DMSO of 2:1. The mixture is stirred for 2 hours to prepare a lead-tin blended perovskite precursor solution with a concentration of 2.4M.

[0051] (5) In a glove box, a one-step spin coating method was used with a rotation speed of 4000 r / min for 40 s. 300 μL of ethyl acetate (EA) was added as an antisolvent in the last 20 s to prepare a perovskite light-absorbing layer. The layer was then annealed on a hot plate at 100 °C for 10 min to obtain a crystallized perovskite light-absorbing layer.

[0052] (6) In a glove box, a 20 nm thick C layer was evaporated on the obtained perovskite light absorption layer in a high vacuum environment by thermal evaporation. 60 Then evaporate a 7nm thick BCP and finally thermally evaporate a 150nm layer of copper as a metal electrode.

[0053] (7) In a nitrogen glove box, the prepared lead-tin blended perovskite solar cells were tested and packaged.

[0054] Figure 3 The performance parameters of different passivation materials for 1200nm thick lead-tin perovskite solar cells were demonstrated. Compared to traditional PEA passivation, CF3-PA passivated 1200nm thick lead-tin perovskite solar cells can fully absorb sunlight and obtain a higher short-circuit current while maintaining a high open-circuit voltage and fill factor, achieving the highest photovoltaic conversion efficiency.

[0055] Figure 4XRD patterns of control, PEA, and CF3-PA perovskites are shown. To demonstrate that 4-trifluorophenylammonium chloride (CF3-PACl) does not form a two-dimensional perovskite in perovskites, large amounts of 4-trifluorophenylammonium chloride (20 mol%) and phenylethylamine chloride (20 mol%) were added to the perovskite precursor. The XRD pattern of the perovskite with 20 mol% 4-trifluorophenylammonium chloride (CF3-PA) is similar to that of the control, indicating that the addition of large amounts of 4-trifluorophenylammonium chloride (CF3-PA) for passivation does not produce a two-dimensional perovskite with poor electrical properties. The introduction of phenylethylamine (PEA) generates a two-dimensional perovskite, which has a different passivation mechanism than 4-trifluorophenylammonium chloride (CF3-PA). Furthermore, the two-dimensional perovskite hinders carrier transport, reducing the short-circuit current density and preventing further improvement in perovskite cell performance.

[0056] Figure 5 The researchers demonstrated that CF3-PA-passivated perovskites possess a longer carrier lifetime and, therefore, a longer carrier diffusion length. In thick absorbance films, fully absorbed sunlight, converted into carriers, can effectively diffuse and transport to both ends of the thick film and inject into the transport layer. However, due to the weaker adsorption capacity of other passivating molecules, they cannot fully cover defects, resulting in insufficient passivation and poor performance of passivated solar cells.

[0057] Figure 6 Demonstrated that at a light intensity of 100mW / cm 2 Current density-voltage curve of large-area lead-tin mixed perovskite solar cell under the following conditions. The active area of the cell is 0.049 cm 2 Test results show that, for lead-tin perovskite solar cells with a 1200nm light-absorbing layer, the efficiency of the unpassivated lead-tin perovskite solar cell is 18.8%, while the efficiency of the lead-tin perovskite solar cell with CF3-PA passivation is 22.2%. This shows that CF3-PA can significantly improve the performance of lead-tin perovskite solar cells with thick light-absorbing layers.

[0058] Figure 7 The JV curves, external quantum efficiency (EQE), and integrated current of lead-tin blend narrow-bandgap solar cells at different thicknesses are shown. For perovskite solar cells passivated with CF3-PA, the short-circuit current density increases with increasing light-absorbing layer thickness. The EQE curves show that increasing thickness leads to a higher EQE in the long-wavelength region, indicating that a greater fraction of long-wavelength sunlight is absorbed and utilized.

Claims

1. A lead-tin blended perovskite film, characterized in that: The lead-tin blended perovskite film is prepared by adding a strong polar passivating agent to a lead-tin blended perovskite precursor solution; The strong polarity passivating agent is selected from one or more of the following compounds: Wherein, X is chlorine, bromine, iodine or fluorine; The lead-tin blended perovskite film is ABX3, where the A position is methylamine ion MA + or formamidinium ion FA + One or a mixture of two of the following: + and tin ions Sn 2+ Blended, and tin ions Sn 2+ The proportion of metal ions is 10%-90%, and the X position is iodide ion I - 、Br - and chloride ions Cl - One or a mixture of two or three.

2. The lead-tin blended perovskite thin film according to claim 1, characterized in that The dosage of the strong polar passivator is 0.01%-10% of the sum of the molar amounts of lead ions and tin ions in the lead-tin blended perovskite precursor.

3. The lead-tin blended perovskite thin film according to claim 2, characterized in that The amount of the strong polar passivator is 0.1%-1% of the sum of the molar amounts of lead ions and tin ions in the lead-tin blended perovskite precursor.

4. The method for preparing a lead-tin blended perovskite thin film according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: preparing a lead-tin blended perovskite precursor solution according to a conventional method; Step 2, adding a strong polar passivating agent to the lead-tin blended perovskite precursor solution, stirring, filtering and waiting for use; Step 3: Prepare a lead-tin blended perovskite film by spin coating, blade coating or spraying the solution obtained in step 2.

5. Use of the lead-tin blended perovskite film according to any one of claims 1 to 3 in the preparation of perovskite solar cells.

6. A perovskite solar cell, characterized in that: A lead-tin blended perovskite film comprising the method according to any one of claims 1 to 3.

7. The perovskite solar cell according to claim 6, characterized in that The thickness of the lead-tin blended perovskite film is 200-2000 nm.

8. The perovskite solar cell according to claim 7, characterized in that The thickness of the lead-tin blended perovskite film is 1000-1500 nm.

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