A surface treatment method of a single-crystal perovskite thin film, a perovskite battery and a preparation method thereof
By using chemical polishing and post-passivation treatment, the problem of high defect density caused by protrusions on the surface of single-crystal perovskite thin films was solved, achieving surface planarization and defect passivation, thereby improving the performance and stability of solar cells.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SUZHOU UNIV
- Filing Date
- 2026-04-08
- Publication Date
- 2026-07-31
AI Technical Summary
The presence of numerous protrusions on the surface of single-crystal perovskite thin films leads to high defect density and inhomogeneity, affecting carrier transport and device performance. Existing polishing or passivation methods cannot effectively address this issue.
Selective polishing of the surface of single-crystal perovskite thin film is performed using a chemical polishing agent solution to remove protrusions. Then, post-passivation is performed using a passivating agent solution to form a smooth passivation layer and reduce the surface defect density.
This study achieved surface planarization and defect suppression of single-crystal perovskite thin films, improved carrier transport uniformity and device stability, and enhanced the photoelectric conversion efficiency and stability of perovskite solar cells.
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Figure CN121985709B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of solar cell fabrication technology, specifically relating to a surface treatment method for single-crystal perovskite thin films, perovskite solar cells, and their fabrication methods. Background Technology
[0002] Metal halide perovskites have attracted much attention in recent years due to their unique and excellent photophysical properties, including high carrier mobility, high defect tolerance, excellent light absorption, and high crystal symmetry, making them a promising next-generation optoelectronic material. However, polycrystalline perovskite films suffer from numerous grain boundaries and high-density charge defects, which weaken device performance and promote moisture erosion and ion migration. In contrast, monocrystalline perovskite films offer significant advantages over polycrystalline perovskite films. Lacking grain boundaries, monocrystalline perovskite films exhibit significantly reduced trap density, significantly enhanced carrier mobility, and superior environmental stability. These inherent properties make monocrystalline perovskite films an ideal candidate for fabricating durable, high-performance solar cells.
[0003] While solution-grown monocrystalline perovskite films offer significant advantages for fabricating large-area monocrystalline perovskite films for photovoltaic applications, rapid evaporation of residual solution during growth can lead to polycrystalline structure formation and impurity deposition, thereby degrading the surface quality of monocrystalline perovskite films. Notably, the surface defect density of monocrystalline perovskite films is approximately four orders of magnitude higher than that of their bulk phase, and can even exceed that of polycrystalline perovskite films. These findings collectively demonstrate that surface optimization of monocrystalline perovskite films is a key factor in the development of high-performance devices. Summary of the Invention
[0004] In view of all or part of the deficiencies of the prior art described above, the purpose of this invention is to provide a surface treatment method for single-crystal perovskite thin films, a perovskite solar cell and its preparation method, which optimizes the surface of single-crystal perovskite thin films and improves the photoelectric conversion efficiency and stability of perovskite solar cells.
[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a perovskite solar cell, comprising the following steps: S1: The bottom electrode and the hole transport layer are sequentially fabricated on the substrate; S2: An initial single-crystal perovskite thin film is grown on the hole transport layer; S3: Apply a chemical polishing agent solution to the surface of the single-crystal perovskite film for chemical polishing. The chemical polishing agent solution does not contain abrasive particles. Polishing is stopped after the surface roughness RMS of the single-crystal perovskite film is less than 5 nm. S4: Apply a passivating agent solution to the surface of the single-crystal perovskite film after chemical polishing for post-passivation; S5: An electron transport layer and a back electrode are sequentially fabricated on the single-crystal perovskite thin film after passivation to obtain a perovskite solar cell.
[0006] The initial surface of a single-crystal perovskite film has protrusions, which are usually impurities (polycrystalline or small single crystals grown from the precursor). Directly removing these protrusions, i.e., the high-defect-density surface, through mechanical polishing can effectively reduce the surface defect density of the single-crystal perovskite film, but it introduces secondary defects such as scratches and lattice dislocations. If only molecular surface passivation is used to remove uncoordinated metal ions such as Pb from the single-crystal perovskite film... 2+ Interactions and halogen vacancy filling can effectively reduce the defect density on the surface of monocrystalline perovskite films, but they cannot eliminate the surface morphology inhomogeneity caused by protrusions, thus impairing the uniformity of carrier transport. Using mechanical polishing or molecular passivation alone to address the surface problems of monocrystalline perovskite films has limitations. This invention first achieves surface planarization of the monocrystalline perovskite film through selective chemical polishing, and then reduces the defect density on the surface through post-passivation. While planarizing the surface, surface defects are also passivated, making it more consistent with the intrinsic characteristics of the monocrystalline perovskite film, laying a solid foundation for constructing high-performance monocrystalline perovskite solar cells.
[0007] Chemical polishing is performed first to selectively and rapidly dissolve microscopic protrusions. These protrusions, with their high free energy and instability, preferentially react with the chemical polishing solution and are removed, thus achieving a smooth and bright surface on the single-crystal perovskite film. This invention utilizes chemical polishing to remove protrusions from the surface of the single-crystal perovskite film. After chemical polishing, pores are created, which are subsequently filled by a passivation layer, further improving the surface smoothness and reducing the surface defect density of the single-crystal perovskite film. In other words, it simultaneously achieves surface planarization and defect suppression. If the chemical polishing solution and passivation solution are mixed and applied simultaneously to the surface of the single-crystal perovskite film, the pores created after chemical polishing cannot be filled by the passivation layer, resulting in ineffective polishing and passivation. The mutual influence and interference between the polishing and passivation processes directly affect the surface morphology of the single-crystal perovskite film, hindering surface planarization and defect suppression. Therefore, this invention stipulates that chemical polishing must be performed before surface passivation; performing them in reverse order or simultaneously will cause serious adverse effects. In contrast to chemical mechanical polishing, chemical polishing requires the addition of abrasive particles, which can scratch the surface of the film.
[0008] This invention addresses the surface treatment of monocrystalline perovskite thin films. On one hand, compared to polycrystalline perovskite films, monocrystalline perovskite films exhibit significantly lower trap density, significantly enhanced carrier mobility, and superior environmental stability. On the other hand, due to grain boundaries and large height differences, chemical polishing of polycrystalline perovskite films has little impact on surface roughness, and passivation cannot achieve excellent flatness and defect suppression. This invention preferably stops chemical polishing when the surface roughness RMS (root mean square deviation) of the monocrystalline perovskite film is less than 5 nm. Surface passivation is then performed after the surface roughness has been optimized to a certain extent (e.g., after obvious protrusions are removed). Compared to direct passivation or passivation while the surface roughness is still large, choosing to passivate when the surface roughness is low results in a smoother film surface, better defect suppression and smoothing effects, and improved uniformity of subsequent carrier transport.
[0009] In step S3, polishing is stopped after chemical polishing until the surface roughness RMS of the single-crystal perovskite film is less than 3 nm; in step S4, a passivation layer is formed on the single-crystal perovskite film by post-passivation treatment, and the surface roughness RMS of the passivation layer is less than 2.5 nm.
[0010] In step S3, the chemical polishing agent solution is a mixed solution of chlorobenzene (CB) and γ-butyrolactone (GBL), with the chlorobenzene accounting for 80%-90% of the total mass of the chemical polishing agent solution. In step S4, the passivating agent solution is a chlorobenzene solution of tetrabutylammonium iodide (TBAI), with the concentration of tetrabutylammonium iodide being 0.5 mg / mL-5 mg / mL. The mass of γ-butyrolactone accounts for 10%-20% of the total mass of the chemical polishing agent solution. More preferably, the mass ratio of chlorobenzene to γ-butyrolactone in the chemical polishing agent solution is 85:15. More preferably, the concentration of tetrabutylammonium iodide in the passivating agent solution is 1 mg / mL. If the concentration of γ-butyrolactone in the chemical polishing agent solution is too low, complete polishing cannot be achieved; if the concentration of γ-butyrolactone is too high, large-area decomposition of the single crystal surface will occur.
[0011] In step S3, the chemical polishing is performed by spin-coating a chemical polishing agent solution at a spin speed of 2000 rpm-4000 rpm for 15-45 seconds. In step S4, the post-passivation is performed by spin-coating a passivating agent solution at a spin speed of 2000 rpm-4000 rpm for 15-45 seconds. The preferred spin speed for the chemical polishing agent solution is 3000 rpm. If the speed is too slow, the single crystal surface is prone to decomposition; if the speed is too fast, complete polishing cannot be achieved.
[0012] In step S2, the single-crystal perovskite film is grown using a spatial confinement method: a prepared perovskite precursor solution is dropped onto the conductive substrate of the hole transport layer, and another conductive substrate is placed on top to form a sandwich structure. The sandwich structure is then heat-treated to allow crystals to crystallize and grow within the sandwich structure, resulting in the single-crystal perovskite film with a thickness of 30-40 micrometers. The spatial confinement method allows for direct growth of single crystals onto a conductive substrate, yielding a single-crystal film with a size of 3-4 millimeters and a thickness of approximately 34 micrometers in about two days.
[0013] The perovskite precursor solution includes methylammonium lead iodide (MAPbI3) and the solvent γ-butyrolactone, wherein the concentration of methylammonium lead iodide in the perovskite precursor solution is 1.2 mol / L-1.8 mol / L; no other additives are added to the perovskite precursor solution.
[0014] The substrate is ITO conductive glass, the bottom electrode is Ag bottom electrode, the electron transport layer is fullerene C60, the back electrode is Ag back electrode, and the raw material solution used for the hole transport layer is poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] with a number average molecular weight of 20,000-50,000; the thickness of the bottom electrode is 80 nm-120 nm, and the thickness of the back electrode is 80-120 nm, preferably around 100 nm.
[0015] The present invention also provides a perovskite battery, which is prepared according to the preparation method of the perovskite battery described above.
[0016] The present invention also provides a surface treatment method for a single-crystal perovskite thin film, comprising: applying a chemical polishing agent solution to the surface of the single-crystal perovskite thin film for chemical polishing, wherein the chemical polishing agent solution does not contain abrasive particles and is a mixed solution composed of chlorobenzene and γ-butyrolactone; and applying a passivating agent solution to the surface of the chemically polished single-crystal perovskite thin film for post-passivation, wherein the passivating agent solution is a chlorobenzene solution of tetrabutylammonium iodide. Attached Figure Description
[0017] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0018] Figure 1 This is a three-dimensional atomic force microscope (AFM) image of a polycrystalline perovskite thin film after polishing.
[0019] Figure 2These are atomic force microscopy (AFM) images of the single-crystal perovskite thin films prepared in Example 1 and Comparative Example 2.
[0020] Figure 3 These are optical microscope images of single-crystal perovskite thin film crystals after chemical polishing in Examples 1, 4, 5 and 6.
[0021] Figure 4 These are optical microscope images of single-crystal perovskite thin film crystals after chemical polishing in Examples 1, 7, 8 and 9.
[0022] Figure 5 These are optical microscope images of single-crystal perovskite thin film crystals after chemical polishing in Example 1 and Comparative Example 3.
[0023] Figure 6 These are steady-state fluorescence (PL) spectra of the single-crystal perovskite films prepared in Example 1 and Comparative Example 1.
[0024] Figure 7 The figures show the current density-voltage curves (JV) of the perovskite solar cells prepared in Example 1 and Comparative Example 1, as well as the test results of the photoelectric conversion efficiency of the perovskite thin film.
[0025] Figure 8 This is a schematic diagram of the treatment of single-crystal perovskite thin films in Example 1.
[0026] Figure 9 This is a schematic diagram of the treatment of single-crystal perovskite thin films in Comparative Example 2.
[0027] Figure 10 These are scanning electron microscope (SEM) images (thickness direction) of the single-crystal perovskite thin films prepared in Example 1 and Comparative Example 1.
[0028] Figure 11 These are optical microscope images of single-crystal perovskite thin film crystals after treatment in Example 1 and Comparative Example 1. Detailed Implementation
[0029] The technical solutions in specific embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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.
[0030] It should be noted that, in order to describe the technical solution more specifically, the steps described in the following embodiments do not strictly correspond one-to-one with the steps described in the invention content section.
[0031] This invention addresses the surface treatment of single-crystal perovskite thin films. The surface roughness difference between polycrystalline perovskite thin films before and after chemical polishing is minimal due to the presence of grain boundaries and significant height differences. Therefore, polishing polycrystalline perovskite thin films is not very effective, and subsequent passivation cannot achieve a smooth surface. Atomic force microscopy (AFM) images of polycrystalline perovskite thin films before and after polishing are shown below. Figure 1 , Figure 1 (a) in the image is before polishing. Figure 1 (b) shows the roughness after polishing. The roughness (Ra) before polishing was 28 nm, and the roughness (Ra) after polishing was 23 nm. See Pan Y, et al. Surface chemical polishing and passivation minimize non-radiative recombination for all-perovskite tandemsolar cells[J]. Nature Communications, 2024, 15(1). Example 1
[0032] A method for preparing a perovskite solar cell includes the following steps: S1: An ITO conductive glass is provided as a substrate. The substrate is a rigid substrate. In this embodiment, the raw material used for the rigid substrate is indium tin oxide. An Ag bottom electrode is fabricated on the substrate, and a hole transport layer is fabricated on the bottom electrode. The raw material solution used for the hole transport layer is poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA material) with a number average molecular weight of 20,000-50,000. The thickness of the bottom electrode is 100 nm. In other embodiments, the materials of the substrate, bottom electrode, and hole transport layer can be freely selected, and the fabrication methods of each layer are existing conventional techniques, which are not described in detail in this application.
[0033] S2: Fabrication of a perovskite layer on the hole transport layer: An initial single-crystal perovskite film is grown on the hole transport layer. In this embodiment, the surface roughness of the initial single-crystal perovskite film is RMS = 11.7 nm. See [link to documentation]. Figure 2(a) The single-crystal perovskite film is grown by a spatial confinement method: a perovskite precursor solution is prepared. In this embodiment, the perovskite precursor solution includes lead methylammonium iodide and the solvent γ-butyrolactone. The concentration of lead methylammonium iodide in the perovskite precursor solution is 1.5 mol / L. No other additives are added to the perovskite precursor solution. The prepared perovskite precursor solution is dropped onto the conductive substrate of the hole transport layer, and another conductive substrate is placed on top to form a sandwich structure. The sandwich structure is heat-treated to allow crystals to crystallize and grow in the middle of the sandwich structure, thereby obtaining the single-crystal perovskite film. The thickness of the single-crystal perovskite film is 34 micrometers. (Reference) Figure 10 (a) In other embodiments, the material of the perovskite layer can be freely chosen. The spatial confinement method is an existing technology, and its process parameters can be adjusted according to actual needs. It will not be described in detail in this application.
[0034] S3: After growth, a chemical polishing agent solution is applied to the surface of the single-crystal perovskite film for chemical polishing. The chemical polishing is performed by spin-coating the chemical polishing agent solution at a speed of 3000 rpm for 30 seconds. In this embodiment, the chemical polishing agent solution is a mixed solution of chlorobenzene and γ-butyrolactone, with a mass ratio of 85:15. The chemical polishing agent solution does not contain abrasive particles. Polishing is stopped when the surface roughness RMS of the single-crystal perovskite film is less than 3 nm. In this embodiment, the surface roughness RMS of the film after chemical polishing is 1.51 nm. See [link to relevant documentation]. Figure 2 (b) In other embodiments, the materials of the chemical polishing agent solution can be adapted, for example, it can also be a mixture of chlorobenzene and N,N-dimethylformamide, etc.
[0035] S4: A passivating agent solution is applied to the surface of the chemically polished single-crystal perovskite film for post-passivation. Post-passivation is performed by spin-coating the passivating agent solution at a speed of 3000 rpm for 30 seconds, resulting in the final single-crystal perovskite film. In this embodiment, the passivating agent solution is a tetrabutylammonium iodide chlorobenzene solution, and the concentration of the tetrabutylammonium iodide is 1 mg / mL. A passivation layer is formed on the single-crystal perovskite film through post-passivation treatment. The surface roughness of the passivation layer is RMS = 0.46 nm. (See [link to documentation]). Figure 2 (c) In this context, after chemical polishing and post-passivation, the thickness of the single-crystal perovskite film decreased from 34 micrometers to 32 micrometers. See [reference needed]. Figure 10 (b) In other embodiments, the material of the passivating agent solution can be adapted, for example, it can also be tetrabutylammonium chloride, tetrabutylammonium bromide or other types of passivating agents.
[0036] S5: An electron transport layer is prepared on the post-passivated single-crystal perovskite thin film. The electron transport layer is fullerene C60 (C60). An Ag back electrode with a thickness of 100 nm is prepared on the electron transport layer to obtain a perovskite solar cell, i.e., a single-crystal perovskite solar cell. CB, GBL, and TBAI used in this embodiment are products of Aladdin Corporation.
[0037] Comparative Example 1 A method for preparing a perovskite solar cell includes the following steps: Step S1 is the same as in Example 1.
[0038] Step S2 is the same as in Example 1. An initial single-crystal perovskite film with a thickness of 34 micrometers is obtained, referenced... Figure 10 (a) in the middle.
[0039] Step S3: An electron transport layer is prepared on the initial single-crystal perovskite thin film. The electron transport layer is fullerene C60 (C60). An Ag back electrode is prepared on the electron transport layer. The thickness of the back electrode is 100 nm, thus obtaining a perovskite solar cell.
[0040] Compared to Example 1, the chemical polishing step and the post-passivation step were omitted.
[0041] Comparative Example 2 Step S1 is the same as in Example 1.
[0042] Step S2 is the same as in Example 1. An initial single-crystal perovskite film is obtained, with a surface roughness RMS = 11.7 nm. See [link to example]. Figure 2 (a) in the middle.
[0043] Step S3: Apply a mixed solution (chemical polishing agent solution + passivating agent solution) to the initial single-crystal perovskite film surface using a spin-coating method at a speed of 3000 rpm for 30 seconds. In this comparative example, the chemical polishing agent solution is a mixed solution of chlorobenzene and γ-butyrolactone, with a mass ratio of 85:15, and does not contain abrasive particles. The passivating agent solution is a chlorobenzene solution of tetrabutylammonium iodide, with a concentration of 1 mg / mL. In this comparative example, the surface roughness RMS of the film after treatment with the mixed solution is 1.36 nm. See [link to relevant documentation]. Figure 2 (d) in the middle.
[0044] Step S4: An electron transport layer is prepared on the single-crystal perovskite thin film. The electron transport layer is fullerene C60. An Ag back electrode is prepared on the electron transport layer. The thickness of the back electrode is 100 nm, thus obtaining a perovskite solar cell.
[0045] Comparative Example 3 Step S1 is the same as in Example 1.
[0046] Step S2 is the same as in Example 1. An initial single-crystal perovskite thin film is obtained.
[0047] Step S3: After growth, a chemical polishing agent solution is applied to the surface of the single-crystal perovskite film for chemical polishing. The chemical polishing is performed by spin-coating the chemical polishing agent solution at a spin speed of 3000 rpm for 30 seconds. In this comparative example, the chemical polishing agent solution is γ-butyrolactone and does not contain abrasive particles.
[0048] Step S4 is the same as in Example 1.
[0049] Step S5 is the same as in Example 1. Example 2
[0050] A perovskite solar cell, prepared according to the preparation method of a perovskite solar cell described in Example 1, is a monocrystalline perovskite solar cell with high surface flatness and low defect density. Example 3
[0051] A surface treatment method for a single-crystal perovskite thin film includes: applying a chemical polishing agent solution to the surface of the single-crystal perovskite thin film for chemical polishing, wherein the chemical polishing agent solution does not contain abrasive particles and is a mixed solution composed of chlorobenzene and γ-butyrolactone; in this embodiment, the preferred mass ratio of chlorobenzene to γ-butyrolactone is 85:15. Chemical polishing is performed by spin-coating the chemical polishing agent solution at a spin speed of 3000 rpm for 30 s. Polishing is stopped after the surface roughness RMS of the single-crystal perovskite thin film is less than 3 nm. A passivating agent solution is then applied to the surface of the chemically polished single-crystal perovskite thin film for post-passivation, wherein the passivating agent solution is a chlorobenzene solution of tetrabutylammonium iodide. In this embodiment, the preferred concentration of tetrabutylammonium iodide in the passivating agent solution is 1 mg / ml. Post-passivation is performed by spin-coating the passivating agent solution at a spin speed of 3000 rpm for 30 s. Example 4
[0052] A method for preparing a perovskite solar cell differs from Example 1 in that, in step S3, the mass ratio of chlorobenzene to γ-butyrolactone in the chemical polishing agent solution is 90:10. Example 5
[0053] A method for preparing a perovskite solar cell differs from Example 1 in that, in step S3, the mass ratio of chlorobenzene to γ-butyrolactone in the chemical polishing agent solution is 80:20. Example 6
[0054] A method for preparing a perovskite solar cell differs from Example 1 in that, in step S3, the mass ratio of chlorobenzene to γ-butyrolactone in the chemical polishing agent solution is 75:25. Example 7
[0055] A method for preparing a perovskite solar cell differs from Example 1 in that, in step S3, the spin-coating speed for chemical polishing is 4000 rpm. Example 8
[0056] A method for preparing a perovskite solar cell differs from Example 1 in that, in step S3, the spin coating speed for chemical polishing is 2000 rpm. Example 9
[0057] A method for preparing a perovskite solar cell differs from Example 1 in that, in step S3, the spin-coating speed for chemical polishing is 1000 rpm.
[0058] refer to Figure 2 , Figure 2 In Example 1, (a) shows the surface roughness of the single-crystal perovskite film before chemical polishing and passivation, with an RMS of 11.7 nm. Figure 2 (b) shows the surface roughness of the single-crystal perovskite film after chemical polishing in Example 1, with an RMS surface roughness of 1.51 nm. Figure 2 (c) shows the surface roughness of the single-crystal perovskite film (actually a passivation layer) after chemical polishing and passivation in Example 1, with a surface roughness RMS = 0.46 nm. Figure 2 In Figure (d), the surface roughness of the single-crystal perovskite film after treatment with the mixed solution in Comparative Example 2 is shown, with an RMS of 1.36 nm. Comparative Example 2 involves the simultaneous addition of chemical polishing agent solution and passivating agent solution. It can be seen that the surface roughness is greater than that after chemical polishing in Example 1. That is, simultaneous addition affects the chemical polishing effect, and because chemical polishing also affects the passivation process, the surface defect density is also affected.
[0059] refer to Figure 3 , Figure 3 Image (a) is an optical microscope image of the thin film crystal after treatment with chemical polishing agent solution CB:GBL = 90:10 in Example 4. Figure 3 Image (b) is an optical microscope image of the thin film crystal after treatment with chemical polishing agent solution CB:GBL = 85:15 in Example 1. Figure 3 Image (c) is an optical microscope image of the thin film crystal after treatment with chemical polishing agent solution CB:GBL = 80:20 in Example 5. Figure 3Image (d) shows an optical microscope image of the thin film crystal after treatment with the chemical polishing agent solution (CB:GBL = 75:25) in Example 6. When CB:GBL = 85:15, the crystal surface is smooth and free of other defects. When CB:GBL = 90:10, the concentration of γ-butyrolactone is too low to achieve complete polishing. When CB:GBL = 80:20, the concentration of γ-butyrolactone is too high, resulting in partial decomposition of the single crystal surface. When CB:GBL = 75:25, the concentration of γ-butyrolactone is too high, resulting in large-area decomposition of the single crystal surface.
[0060] refer to Figure 4 , Figure 4 Image (a) is an optical microscope image of the thin film crystal after treatment (chemical polishing speed 4000 rpm) in Example 7. Figure 4 Image (b) is an optical microscope image of the thin film crystal after treatment (chemical polishing speed 3000 rpm) in Example 1. Figure 4 Image (c) in the image is an optical microscope photograph of the thin film crystal after treatment (chemical polishing speed 2000 rpm) in Example 8. Figure 4 Image (d) shows an optical microscope image of the thin film crystal after treatment (chemical polishing speed 1000 rpm) in Example 9. At a chemical polishing speed of 3000 rpm, the polishing agent can make perfect contact with the single crystal surface, resulting in a smooth crystal surface without other defects. At a chemical polishing speed of 4000 rpm, the polishing agent has difficulty remaining on the single crystal surface, leading to incomplete polishing. At a chemical polishing speed of 2000 rpm, the polishing agent remains on the single crystal surface for too long, resulting in slight decomposition of the single crystal surface. At a chemical polishing speed of 1000 rpm, the polishing agent easily remains on the single crystal surface, and significant decomposition occurs on the single crystal surface.
[0061] refer to Figure 5 , Figure 5 (a) is an optical microscope image (5X) of the thin film crystal after treatment with γ-butyrolactone in Comparative Example 3 (chemical polishing agent solution is γ-butyrolactone). Figure 5 Image (b) is an optical microscope image (5X) of the thin film crystal after treatment with the chemical polishing agent solution (a mixture of chlorobenzene and γ-butyrolactone) in Example 1. When the chemical polishing agent solution contains only γ-butyrolactone, the single crystal surface is completely decomposed.
[0062] Reference Figure 6 and Figure 7 , Figure 6The steady-state fluorescence (PL) spectra of the single-crystal perovskite films prepared in Example 1 and Comparative Example 1 are shown. The steady-state fluorescence intensity of the single-crystal perovskite films of Example 1 and Comparative Example 1 was tested using a 325 nm spectrometer under dark conditions. It can be observed that the PL intensity of the single-crystal perovskite film of Example 1 after chemical polishing and passivation is significantly higher than that of the single-crystal perovskite film of Comparative Example 1 (as a control group) without chemical polishing and passivation, indicating that polishing and post-passivation effectively reduce the defect density. Figure 7 The diagram shows the current density-voltage curves (JV) of the perovskite solar cells prepared in Example 1 and Comparative Example 1, as well as the photoelectric conversion efficiency test results of the perovskite thin films. It can be seen that the photoelectric conversion efficiency of Comparative Example 1 (as a control group) is 12.01%, while that of Example 1 is 19.35%. This invention achieves a significant improvement in photoelectric conversion efficiency by sequentially chemically polishing and passivating the single-crystal perovskite thin film. The open-circuit voltage (VV) of Example 1 is shown in the diagram. OC The voltage is 1.10V, and the short-circuit current density (J) is... SC The value is 24.12 mA / cm. 2 The fill factor (FF) is 72.78%; the open-circuit voltage (V) of Comparative Example 1 is... OC The voltage is 1.03V, and the short-circuit current density (J) is... SC The value is 23.75 mA / cm. 2 The fill factor (FF) is 49.02%. The photoelectric conversion efficiency test results of the perovskite thin film prepared in Comparative Example 2 (with simultaneous application of chemical polishing agent solution and passivator solution) are as follows: The open-circuit voltage (V) of Comparative Example 2... OC The voltage is 1.07V, and the short-circuit current density (J) is... SC The value is 21.10 mA / cm. 2 The fill factor (FF) was 71.39%, and the photoelectric conversion efficiency (PCE) was 16.06%. It can be seen that, compared with the simultaneous application method, the photoelectric conversion efficiency of Example 1, which first applies the chemical polishing agent solution and then applies the passivating agent solution, is significantly higher than that of Comparative Example 2, which applies them simultaneously.
[0063] refer to Figure 8 In Example 1, the initial single-crystal perovskite film (containing impurities on its surface, which are polycrystalline or small single crystals grown from the precursor) was coated with a chemical polishing agent solution, see [link to example]. Figure 8 (a) shows that the protrusions on the surface of the single-crystal perovskite film were removed by chemical polishing. Figure 8 In (b) of the diagram, some uneven areas still exist on the film surface (pores will appear after polishing). A passivating agent solution (TBAI) is then spin-coated for surface passivation, forming a passivation layer on the film surface to fill the pores and make the area uniform, thus creating a highly smooth passivated surface. See [reference needed]. Figure 8(c) in the middle.
[0064] refer to Figure 9 In Comparative Example 2, an initial single-crystal perovskite film (containing impurities on its surface, which were polycrystalline or small single crystals grown from the precursor) was simultaneously spin-coated with a chemical polishing agent solution and a passivating agent solution, as shown in [reference needed]. Figure 9 In (a), the chemical polishing process and the passivation layer formation process occur simultaneously and influence each other. Therefore, after completion, the passivation layer fails to completely cover the film surface, and the pores on the film surface caused by the chemical polishing solution cannot be filled, leaving uneven areas. Figure 9 (b) in the middle.
[0065] Conduct stability testing: refer to Figure 11 , Figure 11 The image shows optical microscope images of the thin film crystals after treatment in Example 1 and Comparative Example 1. Figure 11 In the figures, (a) shows the film of Comparative Example 1 (control group) after 1 day, (b) shows the film of Comparative Example 1 after 3 days, (c) shows the film of Comparative Example 1 after 5 days, (d) shows the film of Example 1 after 1 day, (e) shows the film of Example 1 after 3 days, and (f) shows the film of Example 1 after 5 days. It can be seen that the film crystal of Comparative Example 1 showed slight decomposition after 3 days and obvious decomposition after 5 days, while the film crystal of Example 1 did not decompose after 5 days. Example 1 significantly improved the stability of the single crystal perovskite film. That is, the method of chemical polishing followed by passivation of the present invention can significantly improve the photoelectric conversion efficiency of perovskite solar cells and improve the stability of single crystal perovskite films, thereby improving the stability of perovskite solar cells.
[0066] The above embodiments provide a method for preparing a perovskite solar cell (monocrystalline perovskite solar cell) and a surface treatment method for a monocrystalline perovskite thin film (used for planarization and defect passivation of the monocrystalline perovskite solar cell film). Chemical polishing and post-passivation are used to planarize the surface of the monocrystalline perovskite thin film and reduce the surface defect density. The chemical polishing agent selectively reacts with the protrusions on the surface of the monocrystalline perovskite thin film to planarize it. Subsequently, tetrabutylammonium iodide is used for post-passivation to further planarize the surface of the monocrystalline perovskite thin film. Tetrabutylammonium iodide contains iodine (I) ions, which can react with uncoordinated lead ions (Pb) in the perovskite thin film. 2+Interacting with and filling iodine vacancies effectively reduces surface defects in single-crystal perovskite films. Tetrabutylammonium iodide passivation optimizes the energy level arrangement between the single-crystal perovskite film and the electron transport layer, lowering the interfacial energy barrier and making the single-crystal perovskite film more conducive to electron transport. The hydrophobic properties of tetrabutylammonium iodide effectively prevent water and oxygen from damaging the single-crystal perovskite film, resulting in a more stable film. This invention utilizes chemical polishing and post-passivation to selectively react with the surface of the single-crystal perovskite film, removing surface impurities while reducing the surface defect density, optimizing the surface, and simultaneously improving the photoelectric conversion efficiency and stability of perovskite solar cells.
[0067] The above description of the embodiments is only for the purpose of helping to understand the method and core idea of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.
Claims
1. A method for preparing a perovskite solar cell, characterized in that, Includes the following steps: S1: The bottom electrode and the hole transport layer are sequentially fabricated on the substrate; S2: An initial single-crystal perovskite thin film is grown on the hole transport layer; S3: Apply a chemical polishing agent solution to the surface of the single-crystal perovskite film for chemical polishing. The chemical polishing agent solution does not contain abrasive particles and is a mixed solution composed of chlorobenzene and γ-butyrolactone. The mass of chlorobenzene accounts for 80%-90% of the total mass of the chemical polishing agent solution. Polishing is stopped after the surface roughness RMS of the single-crystal perovskite film is less than 5 nm. S4: Apply a passivating agent solution to the surface of the single-crystal perovskite film after chemical polishing for post-passivation; S5: An electron transport layer and a back electrode are sequentially fabricated on the single-crystal perovskite thin film after passivation to obtain a perovskite solar cell.
2. The method for preparing a perovskite solar cell according to claim 1, characterized in that, In step S3, polishing is stopped after chemical polishing is performed until the surface roughness RMS of the single-crystal perovskite film is less than 3 nm. In step S4, a passivation layer is formed on the single-crystal perovskite film through a post-passivation treatment, and the surface roughness RMS of the passivation layer is less than 2.5 nm.
3. The method for preparing a perovskite solar cell according to claim 1, characterized in that, In step S4, the passivating agent solution is a chlorobenzene solution of tetrabutylammonium iodide, and the concentration of tetrabutylammonium iodide is 0.5 mg / ml-5 mg / ml.
4. The method for preparing a perovskite solar cell according to claim 3, characterized in that, The mass ratio of chlorobenzene to γ-butyrolactone in the chemical polishing agent solution is 85:15; the concentration of tetrabutylammonium iodide in the passivating agent solution is 1 mg / ml.
5. The method for preparing a perovskite solar cell according to claim 1, characterized in that, In step S3, the chemical polishing is performed by spin-coating a chemical polishing agent solution at a spin speed of 2000 rpm-4000 rpm and a spin time of 15-45 s; in step S4, the post-passivation is performed by spin-coating a passivating agent solution at a spin speed of 2000 rpm-4000 rpm and a spin time of 15-45 s.
6. The method for preparing a perovskite solar cell according to claim 1, characterized in that, In step S2, the single-crystal perovskite film is grown by spatial confinement method: a prepared perovskite precursor solution is dropped onto the conductive substrate of the hole transport layer, another conductive substrate is covered to form a sandwich structure, the sandwich structure is heat-treated to allow crystals to crystallize and grow in the middle of the sandwich structure, and the single-crystal perovskite film is obtained. The thickness of the single-crystal perovskite film is 30-40 micrometers.
7. The method for preparing a perovskite solar cell according to claim 6, characterized in that, The perovskite precursor solution comprises methylammonium lead iodide and the solvent γ-butyrolactone, wherein the concentration of methylammonium lead iodide in the perovskite precursor solution is 1.2 mol / L-1.8 mol / L; no other additives are added to the perovskite precursor solution.
8. The method for preparing a perovskite solar cell according to claim 1, characterized in that, The substrate is ITO conductive glass, the bottom electrode is Ag bottom electrode, the electron transport layer is fullerene C60, the back electrode is Ag back electrode, and the raw material solution used for the hole transport layer is poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] with a number average molecular weight of 20,000-50,000; the thickness of the bottom electrode is 80 nm-120 nm, and the thickness of the back electrode is 80-120 nm.
9. A perovskite battery, characterized in that, The perovskite solar cell is prepared according to any one of claims 1-8.
10. A surface treatment method for a single-crystal perovskite thin film, characterized in that, include: A chemical polishing agent solution is applied to the surface of a single-crystal perovskite film for chemical polishing. The chemical polishing agent solution does not contain abrasive particles and is a mixed solution of chlorobenzene and γ-butyrolactone, with the chlorobenzene accounting for 80%-90% of the total mass of the chemical polishing agent solution. After chemical polishing, a passivating agent solution is applied to the surface of the single-crystal perovskite film for post-passivation. The passivating agent solution is a chlorobenzene solution of tetrabutylammonium iodide.