Preparation method and application of 1D / 3D halide perovskite gradient heterojunction

Abstract

The application discloses a preparation method of a 1D / 3D halide perovskite gradient heterojunction and application thereof. The preparation method comprises the following steps: S1, preparing a halide perovskite precursor solution; S2, spin-coating the perovskite precursor solution on a substrate and performing annealing treatment to obtain a 3D perovskite film; S3, dissolving an organic ammonium salt ligand in an isopropyl alcohol solution and fully stirring to obtain a ligand sol; S4, spin-coating the ligand sol on the 3D perovskite film; and S5, performing annealing treatment on the obtained film to obtain a 1D / 3D perovskite heterojunction film. The 1D / 3D halide perovskite gradient heterojunction is simple to prepare, and the content, penetration depth and distribution gradient of the 1D perovskite on the surface of the 3D perovskite film can be adjusted by changing the type of the organic salt ligand anion. When the 1D / 3D perovskite gradient heterojunction is applied to a perovskite solar cell as a light-absorbing layer, the photoelectric conversion efficiency and stability of the perovskite solar cell can be simultaneously improved.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic materials and devices, specifically relating to a method for preparing 1D / 3D halide perovskite gradient heterojunctions and their applications. Background Technology

[0002] Organic halide perovskites are a novel type of photoactive semiconductor material with advantages such as solution-processability, high molar extinction coefficient, high carrier mobility, excellent defect tolerance, and low cost, making them widely used in many fields such as solar cells and light-emitting displays. For example, three-dimensional (3D) halide perovskite thin films are the most commonly used light-absorbing layer material for preparing perovskite solar cells with high photoelectric conversion efficiency. Solution processing is the most common method for preparing halide perovskite thin films. However, the perovskite thin films prepared by this method have a large surface defect state density, which is a significant factor limiting the improvement of solar cell efficiency. Furthermore, 3D perovskite thin films have poor resistance to water and oxygen erosion, severely affecting the stability of solar cells. Therefore, surface modification of 3D perovskite thin films has a crucial impact on improving the photoelectric conversion efficiency and stability of perovskite solar cells. One-dimensional (1D) perovskites have excellent resistance to water and oxygen erosion, and constructing a 1D / 3D perovskite heterojunction light-absorbing layer is an effective method to improve the moisture resistance stability of the cell. Furthermore, by converting impurities such as PbI2 on the surface of 3D perovskites (converting them into 1D perovskites), surface defects can be effectively reduced, improving the photoelectric conversion efficiency of solar cells. However, the poor carrier transport performance of 1D perovskites affects charge transport within the solar cell. Therefore, controlling the 1D / 3D heterojunction structure to obtain a gradient structure with a high 1D perovskite content on the surface and a gradually decreasing content in the deeper layers is crucial to minimizing the adverse effects of 1D perovskites on charge transport.

[0003] 1D perovskites are mainly obtained by reacting the cations in the ligands with residual PbI₂ in the 3D perovskite film. The formation of 1D perovskites is primarily influenced by the cation size and steric hindrance. Currently, the number of organic ligands developed for preparing 1D halide perovskites is very limited, restricted to no more than eight types, including N,N'-dimethyl-substituted imidazoles, trimethylammonium, and tetrabutylammonium. The anions used are limited to halide ions (I₂, I₃, I ... - Cl - Current methods for preparing 1D / 3D heterojunctions mainly employ the organic ammonium cation regulation method (Adv. Funct. Mater., 2021, 31, 2100205), which is heavily limited by the influence of suitable cations. Furthermore, the regulatory effect of cations on the structure of 1D / 3D heterojunctions is limited. Current research primarily focuses on synthesizing novel cationic ligands, with limited research on anionic ligands. Moreover, there are currently no reports on 1D / 3D hierarchical perovskite heterojunctions.

[0004] Therefore, it is essential to develop a method with a wide range of ligand selection and a simple process flow for preparing 1D / 3D perovskite heterojunction thin films with gradient structure characteristics. This is also key to improving the performance of solar cells and light-emitting display devices based on 1D / 3D perovskite heterojunction light-absorbing layers. Summary of the Invention

[0005] In order to overcome the shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing 1D / 3D halide perovskite gradient heterojunctions and their applications.

[0006] The problem to be solved by this invention is: in order to enrich the selection of effective ligands for the synthesis of 1D / 3D perovskite heterojunctions and to find new opportunities for new ligand materials, this invention provides a simple anion-controlled method for preparing 1D / 3D perovskite heterojunction films and effectively controlling the heterojunction structure, as well as a high-efficiency perovskite solar cell based on the light-absorbing layer of the 1D / 3D perovskite gradient heterojunction.

[0007] This invention utilizes tetrabutylammonium salts TBAX (X=F) containing different anions. - ,Cl - ,Br - ,I - CH3COO - BF4 - SCN - By exploiting the differences in bonding strength with the perovskite surface and the rate of 1D perovskite formation, 1D perovskite can be generated on the surface of a 3D perovskite film, constructing a 1D / 3D perovskite heterojunction film and controlling the heterojunction structure. Optimizing suitable anionic TBAX ligands can yield a 1D / 3D perovskite gradient heterojunction thin layer with a high surface 1D perovskite content and a gradually decreasing internal 1D perovskite content. Using this 1D / 3D perovskite gradient heterojunction light-absorbing layer, a perovskite solar cell with high repeatability, high photoelectric conversion efficiency, and high moisture stability (photoelectric conversion efficiency exceeding 20%) was obtained.

[0008] The 1D / 3D perovskite gradient heterojunction film of the present invention is obtained by spin-coating a TBAX organic ammonium salt ligand solution onto the surface of a 3D perovskite and then subjecting it to low-temperature annealing. The reaction rate between the tetrabutyl cation in the ligand and the 3D perovskite surface is adjusted by utilizing the characteristics of anions, thereby achieving the regulation of the 1D / 3D perovskite heterojunction structure.

[0009] The perovskite light-absorbing layer described in this invention is a 1D / 3D perovskite gradient heterojunction thin film.

[0010] The perovskite solar cell of the present invention comprises a transparent conductive substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer, and a metal electrode.

[0011] Preferably, the conductive substrate is FTO or ITO conductive glass.

[0012] Preferably, the electron transport layer is SnO2.

[0013] Preferably, the perovskite light-absorbing layer is a 1D / 3D perovskite gradient heterojunction film.

[0014] Preferably, the hole transport layer is a thin film obtained by spin-coating a mixed solution of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (Spiro-OMeTAD), lithium bis(trifluoromethanesulfonyl)ammonium (LiTFSI), 4-tert-butylpyridine and tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(III)tris[bis(trifluoromethane)sulfonyl ammonium (FK209).

[0015] Preferably, the metal electrode is a gold electrode.

[0016] To achieve the objectives of this invention, the following technical solution is adopted.

[0017] This invention provides a method for preparing 1D / 3D perovskite gradient heterojunction thin films, comprising the following steps:

[0018] (1) Add formamidine iodoformide, chloromethylamine and lead iodide to N,N-dimethylformamide / dimethyl sulfoxide (DMF / DMSO) mixed solvent and stir thoroughly to obtain perovskite precursor solution;

[0019] (2) Spin-coat the perovskite precursor solution obtained in step (1) onto the substrate, and add the antisolvent chlorobenzene before the spin coating is finished, and then anneal in air atmosphere to obtain a 3D perovskite film.

[0020] (3) Add tetrabutylammonium salt TBAX to isopropanol solvent and stir thoroughly to obtain an organic salt ligand solution;

[0021] (4) Spin-coat the ligand solution obtained in step (3) onto the surface of the 3D perovskite film obtained in step (2);

[0022] (5) Anneal the film obtained in step (4) to obtain a 1D / 3D perovskite heterojunction film.

[0023] Further, the molar concentrations of formamidine, lead iodide, and chloromethylamine in step (1) are 1.0-1.8 mol / L, 1.05-1.9 mol / L, and 0.05-0.09 mol / L, respectively. Chloromethylamine plays a role in crystallization regulation, and its addition amount is about 5% of the molar concentration of formamidine.

[0024] Furthermore, the volume ratio of the DMF / DMSO mixed solvent in step (1) is DMF:DMSO = 2:1-5:1.

[0025] Furthermore, the stirring time in step (1) is 5-12 hours.

[0026] More preferably, the molar concentrations of formamidine, lead iodide and chloromethylamine in step (1) are 1.43, 1.5 and 0.07 mol / L, respectively; DMF:DMSO = 4:1; and the stirring time is 6 hours.

[0027] Further, in step (2), the spin coating speed is 4000-6000 rpm, and the spin coating time is 20-40 seconds; the chlorobenzene is added 10-20 seconds before the end of the spin coating, and the amount added is 0.5-1.0 mL. The relative humidity of the air in step (2) is 30-40%. The annealing temperature in step (2) is 120-160℃, and the annealing time is 15-30 minutes.

[0028] More preferably, in step (2), the spin coating speed is 5000 rpm and the spin coating time is 30 seconds; the chlorobenzene is added 15 seconds before the end of the spin coating, and the amount added is 0.75 mL. The relative humidity of the air in step (2) is 35%. The annealing temperature in step (2) is 150°C and the annealing time is 20 minutes.

[0029] Further, the tetrabutylammonium salt TBAX mentioned in step (3) is one or more of tetrabutylammonium fluoride (TBAF), tetrabutylammonium chloride (TBACl), tetrabutylammonium bromide (TBABr), tetrabutylammonium iodide (TBAI), tetrabutylammonium acetate (TBAOOCCH3), tetrabutylammonium fluoroborate (TBABF4), and tetrabutylammonium thiocyanate (TBASCN); its concentration in the organic salt ligand solution is 0.5-5 mg / mL. The stirring time mentioned in step (3) is 0.5-3 hours.

[0030] More preferably, the organic ammonium salt in step (3) is tetrabutylammonium acetate (TBAOOCCH3); its concentration in the organic salt ligand solution is 1.5 mg / mL. The stirring time in step (3) is 1 hour.

[0031] Furthermore, in step (4), the spin coating speed is 2000-5000 rpm and the spin coating time is 10-60 seconds.

[0032] More preferably, the spin coating speed in step (4) is 4000 rpm and the spin coating time is 30 seconds.

[0033] Furthermore, the spin coating atmosphere in step (4) is a nitrogen atmosphere or an air atmosphere.

[0034] Furthermore, the annealing temperature in step (5) is 30-80℃; the annealing time is 10-30 minutes.

[0035] More preferably, the annealing temperature in step (5) is 30°C and the annealing time is 15 minutes.

[0036] This invention provides a 1D / 3D perovskite gradient heterojunction film prepared by the above-described method. Specifically, the 1D / 3D perovskite heterojunction film of this invention is obtained by reacting an organic ammonium salt ligand with the surface of a 3D perovskite, and the 1D / 3D perovskite heterojunction structure is modulated by the type of anion of the organic ammonium salt ligand.

[0037] This invention provides an application of a 1D / 3D perovskite gradient heterojunction thin film for fabricating a light-absorbing layer in a perovskite solar cell. The 1D / 3D perovskite gradient heterojunction thin film is prepared on a substrate containing an electron transport layer according to the above-described preparation method, thus forming the 1D / 3D perovskite heterojunction light-absorbing layer.

[0038] The present invention provides a perovskite solar cell comprising a conductive substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer and a metal electrode stacked sequentially, wherein the perovskite light-absorbing layer is the 1D / 3D perovskite heterojunction light-absorbing layer.

[0039] The present invention provides a method for preparing perovskite solar cells, comprising the following steps:

[0040] (1) Clean the conductive substrate, dry it, spin-coat the electron transport layer paste onto the conductive substrate, and anneal it to obtain the electron transport layer.

[0041] (2) A perovskite light-absorbing layer is prepared on the electron transport layer;

[0042] (3) Spin-coating the hole transport layer solution onto the perovskite light-absorbing layer to obtain the hole transport layer;

[0043] (4) A metal electrode is deposited on the hole transport layer to obtain the perovskite solar cell.

[0044] Further, the conductive substrate in step (1) is FTO conductive glass or ITO conductive glass.

[0045] Further, the electron transport material in step (1) is a dispersion of TiO2, SnO2, ZnO nanoparticles or a PCBM dispersion; the spin coating speed is 3000-5000 rpm, the spin coating time is 20-40 seconds; the annealing temperature is 100-450℃, and the annealing time is 15-60 min.

[0046] More preferably, the electron transport layer material in step (1) is a SnO2 nanoparticle dispersion, the annealing temperature is 180°C, and the annealing time is 15 min.

[0047] Further, the perovskite light-absorbing layer in step (2) is a 1D / 3D perovskite heterojunction light-absorbing layer, which is prepared according to the above preparation method. Specifically, a 1D / 3D perovskite gradient heterojunction film is prepared on a substrate containing an electron transport layer according to the above preparation method, which is the 1D / 3D perovskite heterojunction light-absorbing layer.

[0048] Further, the hole transport layer solution in step (3) is a mixed solution of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (Spiro-OMeTAD), lithium bis(trifluoromethanesulfonyl)ammonium (LiTFSI), 4-tert-butylpyridine and tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(III)tris[bis(trifluoromethane)sulfonyl ammonium (FK209)], wherein the concentration of Spiro-OMeTAD is 73 mM, the concentration of LiTFSI is 42 mM, the concentration of 4-tert-butylpyridine is 55 mM, and the concentration of FK209 is 2.5 mM.

[0049] Furthermore, the metal electrode is a gold electrode (Au).

[0050] This invention employs tetrabutylammonium salt ligands (TBAF, TBACl, TBABr, TBAI, TBAOOCCH3, TBABF4, or TBASCN) spin-coated onto the surface of a 3D perovskite film. The tetrabutylammonium cations react with residual PbI2 on the surface of the 3D perovskite film to generate 1D perovskite, thus obtaining a 1D / 3D perovskite heterojunction film. More importantly, the inventors surprisingly discovered that the anions in the aforementioned ligands have a significant impact on the structure (thickness, 1D perovskite distribution, etc.) of the 1D / 3D perovskite heterojunction. Although the anions in the ligands themselves are not present in the final 1D perovskite composition, they participate in the chemical reaction kinetics of 1D perovskite formation. Based on this discovery, this invention focuses on the influence of anion-controlled methods on the structure of 1D / 3D perovskite heterojunctions: the difference in binding energy between anions and the 3D perovskite surface significantly affects the reaction rate of 1D perovskite formation, ultimately influencing the structure of the 1D / 3D heterojunction. Specifically, the anion properties are utilized to effectively control the content, distribution, and penetration depth of 1D perovskite. The 1D / 3D perovskite heterojunction films prepared by this method exhibit a 1D perovskite gradient distribution characteristic (i.e., high 1D perovskite content on the surface, with a gradually decreasing 1D perovskite content internally). This heterojunction structure can fully leverage the advantages of 1D perovskite and reduce its adverse effects on devices.

[0051] Furthermore, the inventors discovered that different types of anions in the ligands also lead to different 1D perovskite gradient distributions in the 1D / 3D perovskite heterostructure. For example, acetate (CH3COO) - The binding energy between the anion and the 3D perovskite surface is very large. When a tetrabutylammonium acetate (TBAOOCCH3) ligand solution is dropped onto the 3D perovskite surface, the reaction rate with PbI2 on the perovskite surface is very fast, resulting in the rapid formation of a large amount of dense 1D perovskite (TBAPbI3) on the 3D perovskite surface. Because the ligand concentration is rapidly consumed with the reaction, and the dense 1D perovskite hinders the penetration of ligand molecules into the deeper layers of the 3D perovskite, the 1D perovskite content gradually decreases from the surface to the depths within the heterojunction (i.e., exhibiting a 1D perovskite gradient distribution characteristic).

[0052] Furthermore, the thickness decreases rapidly, resulting in a small gradient heterojunction thickness. When the binding force between the anion in the ligand and the perovskite surface is weak (e.g., I...), - SCN - The reaction rate for generating 1D perovskite is small, resulting in a relatively low content of 1D perovskite on the surface and a large penetration layer depth (i.e., a large thickness of 1D / 3D gradient heterojunction).

[0053] In solar cell applications, heterojunction structures employing a high 1D perovskite content on the surface with a rapidly decreasing gradient distribution over a relatively small thickness range can endow perovskite solar cells with excellent overall performance. The high 1D perovskite content on the surface efficiently passivates surface defects in 3D perovskite and gives the perovskite excellent resistance to water and oxygen corrosion, resulting in good stability. Meanwhile, the gradually decreasing 1D perovskite content internally minimizes its adverse effects on charge transport, ensuring the cell still maintains excellent photoelectric conversion efficiency. Under the preferred conditions of this invention, in the 1D / 3D gradient heterojunction prepared using TBAOOCCH3 ligands, the 1D perovskite content on the heterojunction surface reaches as high as 47.7%, rapidly decreasing to 8.2% within a 25nm thickness range. When this 1D / 3D perovskite gradient heterojunction is used as a light-absorbing layer in a perovskite solar cell, the cell achieves a photoelectric conversion efficiency of 20.1% and excellent moisture stability. After being stored for 1000 hours in an environment with a relative humidity of 30±5%, the cell still maintains an initial efficiency of over 92%.

[0054] The method for preparing 1D / 3D perovskite gradient heterojunction thin films according to this invention features simple process, mild reaction conditions, easy reproducibility, and low cost, which is conducive to the application and promotion of the technology. When the 1D / 3D perovskite gradient heterojunction thin film prepared by this invention is used as the light-absorbing layer of perovskite solar cells, the preparation process is simple and the processing temperature is low, while improving the photoelectric conversion efficiency and stability of perovskite solar cells, which is beneficial to the industrial production of perovskite solar cells.

[0055] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0056] (1) In the preparation method of 1D / 3D perovskite gradient heterojunction thin film provided by the present invention, the technology of using the anion of tetrabutylammonium ligand to regulate the kinetic process of 1D perovskite formation and thereby regulate the 1D / 3D perovskite heterojunction structure can greatly expand the range of organic ligand materials for preparing 1D / 3D perovskite heterojunction.

[0057] (2) In the preparation method of 1D / 3D perovskite gradient heterojunction thin film provided by the present invention, the organic ammonium salt anion used is a commonly used inorganic anion, which is non-toxic, non-irritating, environmentally friendly and low in cost, which is conducive to the promotion of the technology.

[0058] (3) The preparation method of 1D / 3D perovskite gradient heterojunction thin film provided by the present invention has a simple preparation process and low processing temperature, which is beneficial for preparing thin films and devices on different substrates.

[0059] (4) In the method for preparing 1D / 3D perovskite gradient heterojunctions of the present invention, the structural characteristics such as the density and content gradient of 1D perovskite on the surface of the gradient heterojunction and the thickness of the heterojunction can be effectively controlled by changing the type of anion, which can be applied to different application fields and application environments with different performance requirements.

[0060] (5) The process provided by this invention is simple, reproducible, and low-cost, offering a new feasibility for preparing high-efficiency and stable perovskite solar cells. The 1D / 3D perovskite gradient heterojunction thin film of this invention also has broad application prospects in other photovoltaic devices, optoelectronic devices, and light-emitting displays. Attached Figure Description

[0061] Figure 1 These are scanning electron microscope images of the surface of the 3D perovskite thin film prepared in Example 1.

[0062] Figure 2 This is the X-ray diffraction pattern of the 3D perovskite thin film prepared in Example 1.

[0063] Figure 3 These are scanning electron microscope images of the surface of the 1D / 3D perovskite gradient heterojunction thin film prepared in Example 2.

[0064] Figure 4 The X-ray diffraction pattern is that of the 1D / 3D perovskite gradient heterojunction thin film prepared in Example 2.

[0065] Figure 5 The X-ray photoelectron spectroscopy (XPS) of the 1D / 3D perovskite gradient heterojunction thin film prepared in Example 2 is shown.

[0066] Figure 6 These are scanning electron microscope images of the surface of the 1D / 3D perovskite gradient heterojunction thin film prepared in Example 3.

[0067] Figure 7 The X-ray diffraction pattern is that of the 1D / 3D perovskite gradient heterojunction thin film prepared in Example 3.

[0068] Figure 8 The X-ray photoelectron spectroscopy (XPS) of the 1D / 3D perovskite gradient heterojunction thin film prepared in Example 3 is shown.

[0069] Figure 9 This is an X-ray photoelectron spectroscopy image of the 1D / 3D perovskite gradient heterojunction thin film prepared in Example 4.

[0070] Figure 10 This is the JV curve of the perovskite solar cell prepared in Example 5.

[0071] Figure 11 This is the stability curve of the perovskite solar cell prepared in Example 5.

[0072] Figure 12 This is the JV curve of the perovskite solar cell prepared in Example 6.

[0073] Figure 13 This is the stability curve of the perovskite solar cell prepared in Example 6.

[0074] Figure 14 This is the JV curve of the perovskite solar cell prepared in Example 7.

[0075] Figure 15 This is the stability curve of the perovskite solar cell prepared in Example 7.

[0076] Figure 16 This is the JV curve of the perovskite solar cell prepared in Example 8.

[0077] Figure 17 This is the stability curve of the perovskite solar cell prepared in Example 8. Detailed Implementation

[0078] The specific implementation of the present invention will be further described below with reference to embodiments and accompanying drawings, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to existing technology. Reagents or instruments whose manufacturers are not specified are considered to be conventional products that can be purchased commercially.

[0079] Example 1

[0080] Preparation of 3D perovskite thin films:

[0081] 0.8805 g of lead iodide (PbI₂), 0.3095 g of formamidine iodide (FAI), and 0.0425 g of chloromethylamine (MACl) were dissolved in a mixed solution of 0.8 mL of DMF and 0.2 mL of DMSO. The solution was stirred for 6 hours until fully dissolved to obtain a perovskite precursor solution. Before use, the precursor solution was filtered through a 0.22 μm TPFE membrane. In a nitrogen glove box, 60 μL of the perovskite precursor solution was dropped onto a clean FTO glass substrate (1.5 cm × 1.5 cm). The substrate was spin-coated at 5000 rpm for 30 seconds. At the 15th second, 750 μL of chlorobenzene was rapidly added to the film to obtain a perovskite precursor film. The perovskite precursor film was transferred to an air glove box with a relative humidity of 30% and annealed on a hot plate at 150 °C for 20 minutes to obtain a 3D perovskite film with a thickness of approximately 750 nm. Scanning electron microscopy shows ( Figure 1 The prepared 3D perovskite films are compact and dense, with a smooth surface and grain size between 1 and 3 μm. X-ray diffraction results show that ( Figure 2 The prepared 3D perovskite is α-FAPbI3 and has excellent crystallinity. The diffraction peak at 12.7° indicates that there is a lot of residual PbI2 in the perovskite film.

[0082] Example 2

[0083] Preparation of 1D / 3D perovskite gradient heterojunction films:

[0084] (1) Preparation of 3D perovskite thin films: Same as in Example 1

[0085] (2) Preparation of 1D / 3D perovskite heterojunction films:

[0086] 2.0 mg of tetrabutylammonium chloride (TBACl) was dissolved in 1 mL of anhydrous isopropanol and stirred for 1 hour to obtain a clear TBACl / isopropanol solution. 40 μL of the TBACl / isopropanol solution was dropped onto a 3D perovskite film and spin-coated at 4000 rpm for 30 seconds. The resulting film was annealed on a hot plate at 50 °C for 10 minutes to obtain a 1D / 3D perovskite heterojunction film with a thickness of approximately 750 nm. Scanning electron microscopy showed (…). Figure 3 The 1D / 3D perovskite heterojunction films prepared using TBACl ligands are dense and uniform. Compared with 3D perovskite films, the 1D / 3D perovskite heterojunctions exhibit fine particles with a diameter of 5-15 nm on their surface. X-ray diffraction patterns ( Figure 4The decrease in relative intensity of the diffraction peak at 12.7° indicates a reduction in PbI2 residue. Simultaneously, the diffraction peak at 7.2° indicates that the fine particles on the film surface are 1D TBAPbI3 perovskite. X-ray photoelectron spectroscopy analysis shows that... Figure 5 The average proportion of 1D TBAPbI3 perovskite in the shallow layer (thickness of about 0-3 nm) of the heterostructure (1D / (1D+3D)) was 36.1%, the average proportion in the thickness of about 0-8 nm was 33.5%, and the average proportion in the thickness range of 20-25 nm from the surface was 12.7%. This indicates that a 1D / 3D perovskite gradient heterostructure was successfully prepared using TBACl. The 1D perovskite content was the highest at the surface, and then it showed a slow decrease in distribution over a larger thickness range.

[0087] Example 3

[0088] Preparation of 1D / 3D perovskite heterojunction thin films:

[0089] (1) Preparation of 3D perovskite thin film: Same as in Example 1.

[0090] (2) Preparation of 1D / 3D perovskite gradient heterojunction thin films:

[0091] 1.5 mg of tetrabutylammonium acetate (TBAOOCCH3) was dissolved in 1 mL of anhydrous isopropanol and stirred for 1 hour to obtain a clear TBAOOCCH3 / isopropanol solution. 40 μL of the TBAOOCCH3 / isopropanol solution was dropped onto a 3D perovskite film and spin-coated at 4000 rpm for 30 seconds. The resulting film was then placed at 30°C for 15 minutes to obtain a 1D / 3D perovskite heterojunction film with a thickness of approximately 750 nm. Scanning electron microscopy showed… Figure 6 The 1D / 3D perovskite heterostructure films prepared using TBAOOCCH3 ligands are dense and uniform, with fine particles of 5-10 nm in diameter on the surface. X-ray diffraction pattern ( Figure 7 The diffraction peak at 12.7° shows a significant decrease in relative intensity, indicating a substantial reduction in PbI2 residue. Simultaneously, the diffraction peak at 7.2° indicates that the fine particles on the film surface are 1D TBAPbI3 perovskite. X-ray photoelectron spectroscopy analysis shows that... Figure 8The average percentage (1D / (1D+3D)) of 1D TBAPbI3 perovskite in the shallow layer (approximately 0–3 nm thickness) of the heterojunction is 47.7%, the average percentage in the 0–8 nm thickness is 30.6%, and the average percentage in the 20–25 nm thickness range from the surface is 8.2%. This indicates that the 1D / 3D perovskite heterojunction prepared using TBAPbI3 has a gradient distribution structure of 1D perovskite. The 1D perovskite content is high at the surface and exhibits a rapidly decreasing gradient distribution within a relatively small thickness range, forming a thin 1D / 3D perovskite heterojunction layer. This gradient heterojunction structure is more conducive to passivating surface defects of 3D perovskite, resisting water vapor erosion, and minimizing the adverse effects of 1D perovskite on carrier transport.

[0092] Example 4

[0093] Preparation of 1D / 3D perovskite heterojunction thin films:

[0094] (1) Preparation of 3D perovskite thin film: Same as in Example 1.

[0095] (2) Preparation of 1D / 3D perovskite heterojunction films:

[0096] 5.0 mg of tetrabutylammonium thiocyanate (TBASCN) was dissolved in 1 mL of anhydrous isopropanol and stirred for 1 hour to obtain a clear TBASCN / isopropanol solution. 40 μL of the TBASCN / isopropanol solution was dropped onto a 3D perovskite film and spin-coated at 5000 rpm for 30 seconds. The resulting film was annealed at 80 °C for 10 minutes to obtain a 1D / 3D perovskite heterojunction film with a thickness of approximately 750 nm. Scanning electron microscopy and X-ray diffraction showed that the morphology and crystal structure of the 1D / 3D perovskite heterojunction prepared using TBASCN ligand were similar to those of the heterojunction prepared using TBACl and TBAOOCCH3. X-ray photoelectron spectroscopy analysis showed that... Figure 9 The average proportion (1D / (1D+3D)) of 1D TBAPbI3 perovskite in the shallow layer (thickness of about 0-3 nm) of the heterojunction was 30.1%, the average proportion in the thickness of about 0-8 nm was 28.7%, and the average proportion in the thickness range of 20-25 nm from the surface was 17.8%. This shows that 1D / 3D perovskite gradient heterojunctions can also be prepared using TBASCN. The results of this example are similar to those of Example 2. The 1D perovskite content is the highest at the surface and then slowly decreases over a larger thickness range. However, the 1D perovskite content at the surface is much lower than that of the heterojunction prepared using TBAOOCCH3. This is because the different types of anions in the ligands affect the reaction rate of 1D perovskite formation, resulting in different 1D perovskite gradient distributions.

[0097] Example 5

[0098] (1) Cleaning of ITO conductive glass substrate:

[0099] The ITO conductive glass was ultrasonically cleaned with glass cleaner, deionized water, acetone, and ethanol, and finally dried with nitrogen to obtain a clean ITO conductive glass substrate.

[0100] (2) Preparation of SnO2 electron transport layer:

[0101] A commercially available SnO2 nanoparticle dispersion (15% by mass) was diluted to 3% with deionized water, ultrasonicated for 10 minutes, and then filtered through a 0.22 μm TPFE aqueous filter membrane. The SnO2 dispersion was spin-coated onto a clean ITO substrate at 3000 rpm using a spin coater, and then annealed at 180 °C for 15 min to obtain a dense SnO2 electron transport layer. The thickness of the electron transport layer was 50 nm.

[0102] (3) Preparation of 3D perovskite light-absorbing layer: Same as in Example 1. The thickness of the 3D perovskite light-absorbing layer is 750 nm.

[0103] (4) Preparation of the hole transport layer:

[0104] A hole transport layer solution was prepared by dissolving 90 mg of Spiro-OMeTAD (2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene) in 1 mL of chlorobenzene. After stirring for 3 h, 39.5 μL of 4-tert-butylpyridine, 23 μL of lithium salt solution (520 mg of lithium bis(trifluoromethanesulfonyl)ammonium dissolved in 1 mL of acetonitrile), and 10 μL of cobalt salt solution (375 mg of FK209-Co(III)-TFSI cobalt dissolved in 1 mL of acetonitrile) were added sequentially to obtain the hole transport layer solution. The hole transport layer solution was spin-coated onto a perovskite light-absorbing layer using a spin coater at a speed of 5000 rpm. The thickness of the hole transport layer was approximately 180 nm.

[0105] (5) Preparation of metal electrodes:

[0106] The sample with the hole transport layer spin-coated is placed in a vacuum thermal evaporation equipment to deposit an 80nm thick gold electrode, thus obtaining a perovskite solar cell.

[0107] (6) Testing: At AM1.5 standard, 100mW·cm -2 Under light intensity, the effective active layer area is 0.09 cm². 2 The photoelectric performance of perovskite solar cells was tested. For example... Figure 10 As shown, the photoelectric performance parameters of this battery are: open-circuit voltage 0.98V, short-circuit current density 23.78mA·cm⁻¹. -2The fill factor is 0.788, and the photoelectric conversion efficiency is 18.2%. This indicates that the performance of the perovskite solar cell prepared using a pure 3D perovskite light-absorbing layer is generally poor. Cell stability test results ( Figure 11 The results showed that after the unencapsulated battery was placed in an air environment with a relative humidity of 35±5% for 1000 hours, the photoelectric conversion efficiency rapidly decreased to 46% of the initial efficiency, indicating that the battery prepared with a pure 3D perovskite light-absorbing layer has poor moisture resistance.

[0108] Example 6

[0109] (1) Cleaning of ITO conductive glass substrate: Same as in Example 5.

[0110] (2) Preparation of SnO2 electron transport layer: Same as in Example 5.

[0111] (3) Preparation of 1D / 3D perovskite heterojunction light-absorbing layer: Same as in Example 2. The thickness of the 1D / 3D perovskite heterojunction light-absorbing layer is 750 nm.

[0112] (4) Preparation of hole transport layer: Same as in Example 5.

[0113] (6) Preparation of metal electrodes: Same as in Example 5.

[0114] (7) Test: At AM1.5 standard, 100mW·cm -2 Under light intensity, the effective active layer area is 0.09 cm². 2 The photoelectric performance of perovskite solar cells was tested. For example... Figure 12 As shown, the photoelectric performance parameters of this battery are: open-circuit voltage 1.0V, short-circuit current density 24.02mA·cm⁻¹. -2 The fill factor is 0.806, and the photoelectric conversion efficiency is 19.5%. Stability tests show that ( Figure 13 After being placed in an air environment with a relative humidity of 35±5% for 1000 hours, the photoelectric conversion efficiency of the unencapsulated battery rapidly decreased to 82% of the initial efficiency. This indicates that the 1D / 3D perovskite gradient heterojunction light-absorbing layer prepared by the TBACl ligand in this invention can effectively improve the photoelectric conversion efficiency and moisture resistance of perovskite solar cells.

[0115] Example 7

[0116] (1) Cleaning of ITO conductive glass substrate: Same as in Example 5.

[0117] (2) Preparation of SnO2 electron transport layer: Same as in Example 5.

[0118] (3) Preparation of 1D / 3D perovskite heterojunction light-absorbing layer: Same as in Example 4. The thickness of the 1D / 3D perovskite heterojunction light-absorbing layer is 750 nm.

[0119] (4) Preparation of hole transport layer: Same as in Example 5.

[0120] (6) Preparation of metal electrodes: Same as in Example 5.

[0121] (7) Test: At AM1.5 standard, 100mW·cm -2 Under light intensity, the effective active layer area is 0.09 cm². 2 The photoelectric performance of perovskite solar cells was tested. For example... Figure 14 As shown, the photoelectric performance parameters of this battery are: open-circuit voltage 1.0V, short-circuit current density 23.89mA·cm⁻¹. -2 The fill factor was 0.791, and the photoelectric conversion efficiency was 18.9%. Stability tests showed that after the unencapsulated battery was placed in an air environment with a relative humidity of 35±5% for 1000 hours, the photoelectric conversion efficiency rapidly decreased to 65% of the initial efficiency. Figure 15 This invention demonstrates that the 1D / 3D perovskite gradient heterojunction light-absorbing layer prepared using TBASCN can improve the photoelectric conversion efficiency and moisture resistance of perovskite solar cells to a certain extent.

[0122] Example 8

[0123] (1) Cleaning of ITO conductive glass substrate: Same as in Example 5.

[0124] (2) Preparation of SnO2 electron transport layer: Same as in Example 5.

[0125] (3) Preparation of 1D / 3D perovskite gradient heterojunction light-absorbing layer: Same as in Example 3. The thickness of the 1D / 3D perovskite heterojunction light-absorbing layer is 750 nm.

[0126] (4) Preparation of hole transport layer: Same as in Example 5.

[0127] (6) Preparation of metal electrodes: Same as in Example 5.

[0128] (7) Test: At AM1.5 standard, 100mW·cm -2 Under light intensity, the effective active layer area is 0.09 cm². 2 The photoelectric performance of perovskite solar cells was tested. For example... Figure 16 As shown, the photoelectric performance parameters of the battery are: open-circuit voltage 1.02V, short-circuit current density 23.99mA·cm⁻¹. -2 The fill factor is 0.819, and the photoelectric conversion efficiency is 20.1%. Stability tests show that the unencapsulated battery retains 92% of its initial efficiency after being placed in an air environment with a relative humidity of 35±5% for 1000 hours. Figure 17Compared to the perovskite solar cells prepared in Examples 6 and 7, the perovskite solar cell prepared using a 1D / 3D perovskite gradient heterojunction light-absorbing layer with high 1D perovskite surface content and a rapidly decreasing internal structure achieves higher photoelectric conversion efficiency and moisture resistance. This is because a higher 1D perovskite surface content is beneficial for passivating 3D perovskite surface defects, resisting moisture erosion, and thus improving stability. Furthermore, the rapidly decreasing internal 1D perovskite content has a smaller adverse effect on charge transport compared to a slowly decreasing content, resulting in higher photoelectric conversion efficiency.

[0129] Examples 6-8 demonstrate that when the 1D / 3D perovskite gradient heterojunction with 1D perovskite gradient distribution characteristics prepared according to this invention is used as a light-absorbing layer in perovskite solar cells, both the photoelectric conversion efficiency and moisture resistance of the cells can be improved. This indicates that optimizing the 1D / 3D perovskite heterojunction structure using anion modulation technology is an effective method to obtain high efficiency and high stability.

Claims

1. A method for preparing a 1D / 3D perovskite gradient heterojunction, characterized in that, Includes the following steps: (1) Add formamidine iodoformide, chloromethylamine and lead iodide to a DMF / DMSO mixed solvent and stir thoroughly to obtain a perovskite precursor solution; (2) Spin-coat the perovskite precursor solution obtained in step (1) onto the substrate, and add the antisolvent chlorobenzene before the spin coating is finished, and then anneal in air atmosphere to obtain 3D perovskite film. (3) Add tetrabutylammonium salt TBAX to isopropanol solvent and stir thoroughly to obtain an organic salt ligand solution; the tetrabutylammonium salt TBAX is tetrabutylammonium acetate TBAOOCCH3, and its concentration in the organic salt ligand solution is 0.5-5 mg / mL; (4) Spin-coat the ligand solution obtained in step (3) onto the surface of the 3D perovskite film obtained in step (2); (5) Anneal the film obtained in step (4) to obtain a 1D / 3D perovskite heterojunction film.

2. The method for preparing a 1D / 3D perovskite gradient heterojunction according to claim 1, characterized in that, The molar concentrations of formamidine, lead iodide and chloromethylamine in step (1) are 1.0-1.8 mol / L, 1.05-1.9 mol / L and 0.05-0.09 mol / L, respectively; the volume ratio of the DMF / DMSO mixed solvent in step (1) is DMF:DMSO=2:1-5:1; the stirring time in step (1) is 5-12 hours.

3. The method for preparing a 1D / 3D perovskite gradient heterojunction according to claim 1, characterized in that, The spin coating speed in step (2) is 4000-6000 rpm, and the spin coating time is 20-40 seconds; the chlorobenzene is added 10-20 seconds before the end of the spin coating, and the amount added is 0.5-1.0 mL; the annealing temperature in step (2) is 120-160℃, and the annealing time is 15-30 minutes.

4. The method for preparing a 1D / 3D perovskite gradient heterojunction according to claim 1, characterized in that, The stirring time in step (3) is 0.5-3 hours.

5. The method for preparing a 1D / 3D perovskite gradient heterojunction according to claim 1, characterized in that, The spin coating speed in step (4) is 2000-5000 rpm, and the spin coating time is 10-60 seconds; the spin coating atmosphere is nitrogen or air.

6. The method for preparing a 1D / 3D perovskite gradient heterojunction according to claim 1, characterized in that, The annealing temperature in step (5) is 30-80℃, and the annealing time is 10-30 minutes.

7. A 1D / 3D perovskite gradient heterojunction thin film prepared by the preparation method according to any one of claims 1-6.

8. A method for preparing a 1D / 3D perovskite heterojunction light-absorbing layer, characterized in that, A 1D / 3D perovskite gradient heterojunction thin film is prepared on a substrate containing an electron transport layer according to the preparation method described in any one of claims 1-6, which is a 1D / 3D perovskite heterojunction light-absorbing layer.

9. A perovskite solar cell, comprising a conductive substrate, an electron transport layer, a perovskite light-absorbing layer, a hole transport layer, and a metal electrode stacked sequentially, characterized in that, The perovskite light-absorbing layer is a 1D / 3D perovskite heterojunction light-absorbing layer obtained by the preparation method described in claim 8.

10. A method for preparing the perovskite solar cell according to claim 9, characterized in that, Includes the following steps: (1) Clean the conductive substrate, blow dry, spin coat the electron transport layer paste onto the conductive substrate, and anneal to obtain the electron transport layer; the conductive substrate is FTO conductive glass or ITO conductive glass; The electron transport layer material is one or more of TiO2, SnO2, ZnO, and PCBM; (2) A perovskite light-absorbing layer is prepared on the electron transport layer; the perovskite light-absorbing layer is a 1D / 3D perovskite gradient heterojunction light-absorbing layer; (3) The hole transport layer solution is spin-coated onto the perovskite light-absorbing layer to obtain the hole transport layer; the hole transport layer solution is a mixed solution of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene, lithium bis(trifluoromethanesulfonate), 4-tert-butylpyridine and tri(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(III)tri[bis(trifluoromethane)sulfonylimide]; (4) A metal electrode is deposited on the hole transport layer to obtain the perovskite solar cell.

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