A method for in-plane directional crystallization of halide perovskite

Abstract

The present invention belongs to the field of halide perovskite semiconductors, and discloses a method for directional crystallization of halide perovskite in a plane, the method comprising the following steps: (1) preparing a perovskite precursor; (2) coating the perovskite precursor on a substrate to obtain a precursor wet film; (3) by regulating the volatilization position and volatilization direction of the solvent in the precursor wet film, controlling the precursor wet film to be preferentially supersaturated in a single selected local area, achieving localized nucleation at a controllable position, while inhibiting nucleation at other positions, establishing a radial in-plane concentration gradient, achieving directional continuous growth in the plane, and thus obtaining a halide perovskite film with localized nucleation and continuous growth. The present invention regulates the volatilization position and volatilization direction of the solvent in the precursor wet film, first causing localized nucleation, and then causing in-plane directional continuous growth, and can achieve controllable preparation of high-quality halide perovskite films.

Description

Technical Field

[0001] The present invention belongs to the field of halide perovskite semiconductors, and more specifically, relates to a method for in-plane directional crystallization of halide perovskites, which can achieve localized nucleation and in-plane directional crystallization, thereby obtaining in-plane directional and continuously grown halide perovskite materials. Background Art

[0002] As human activities affect the global climate, the impact of the climate crisis is becoming increasingly widespread and serious, almost everywhere. At the same time, the shortage of traditional energy is gradually threatening human survival and development. In response to these problems, China announced to the world the goal of achieving carbon peak by 2030 and carbon neutrality by 2060. Under this trend, the development of new energy, especially photovoltaic technology, has become the most critical link.

[0003] Metal halide perovskite materials have the advantages of high efficiency, low cost and solution preparation, and have attracted the attention of academia and industry. In just over a decade, the certified photoelectric conversion efficiency of perovskite solar cells has rapidly increased from the initial 3.8% to 25.7%, which is very close to that of crystalline silicon solar cells, and is expected to achieve parity or even cheap photovoltaic power generation costs.

[0004] In halide perovskite semiconductor materials, excellent crystallization and good morphology are the basis for ensuring the excellent performance of semiconductor materials. Based on halide perovskite solar cells, a large amount of research work revolves around optimizing the crystallization and morphology of halide perovskite films. The most widely used methods are anti-solvent method, continuous deposition method, hot coating method, blowing method and vacuum method, but these methods obtain a large number of crystal nuclei and small grain size, resulting in more grain boundaries between grains, and each film prepared has a great difference. As for the spatial confinement inversion growth process for preparing large-sized grains, its disadvantage is that the prepared perovskite is still in the liquid phase solvent, which requires effective treatment to ensure its crystal quality, thereby limiting its application. The previous results of the inventor's research group, "A method for preparing high-quality halide perovskite films" (Chinese patent application CN113788629A), through the controllable and slow removal of solvent in a confined space, reduce the formation of crystal nuclei, and balance the growth of crystal nuclei with the volatilization of solvent, which helps to obtain high-quality perovskite films with fully grown crystals. However, in this method, the formation of crystal nuclei is random and may appear at any position in the film, which makes the controllable preparation of large-area high-quality perovskite films challenging. Therefore, it is of great significance to develop a more controllable technology to achieve the controllable preparation of large-area high-quality perovskite films. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the object of the present invention is to provide a method for in-plane directional crystallization of halide perovskite, wherein by regulating the volatilization position and volatilization direction of the solvent in the precursor wet film, positioned nucleation occurs first, and then in-plane directional continuous growth occurs, thereby achieving controllable preparation of high-quality halide perovskite thin films, and further improving the quality of the prepared halide perovskite thin films through in-plane directional crystallization, providing strong support for the preparation of high-performance halide perovskite optoelectronic devices.

[0006] To achieve the above object, the present invention provides a method for directional crystallization of halide perovskite in-plane, characterized in that it comprises the following steps:

[0007] (1) adding a monovalent salt and a divalent metal salt to a solvent to obtain a perovskite precursor; the monovalent salt and the divalent metal salt are both halogen salts or pseudo-halogen salts;

[0008] (2) coating the perovskite precursor obtained in step (1) on a substrate to obtain a precursor wet film;

[0009] (3) By regulating the evaporation position and evaporation direction of the solvent in the precursor wet film, the precursor wet film is controlled to be preferentially supersaturated in a single selected local area, thereby achieving localized nucleation at a controllable position and inhibiting nucleation at other positions, thereby establishing a radial in-plane concentration gradient and achieving directional continuous growth within the plane, thereby obtaining a halide perovskite film with localized nucleation and continuous growth.

[0010] As a further preferred embodiment of the present invention, in step (3), the volatilization position and volatilization direction of the solvent in the precursor wet film are regulated, specifically:

[0011] The precursor wet film is placed in a closed space for heating, the precursor wet film only contacts the substrate located below, and does not contact the inner cavity side wall and top surface of the closed space; the closed space has only one single exhaust port at a pre-selected position, or a group of exhaust port arrays; and for this group of exhaust port arrays, the shortest distance between the edges of two adjacent exhaust ports does not exceed 20 mm, so that this group of exhaust port arrays can correspond to a whole exhaust port area;

[0012] Due to the setting of the exhaust port, the saturated vapor generated by the heating of the precursor wet film in the confined space will be discharged from the exhaust port first, so that the wet film area corresponding to the exhaust port will reach supersaturation first and position nucleation will occur; at the same time, a radial solvent vapor gradient pointing to the exhaust port will be formed in the confined space, so that a radial in-plane concentration gradient will also be formed in the wet film surface, thereby realizing the radial directional continuous growth of halide perovskite in the surface.

[0013] As a further preferred embodiment of the present invention, there is a gap between the top surface of the inner cavity of the enclosed space and the upper surface of the precursor wet film, and the spacing of the gap is less than 5% of the length of the precursor wet film.

[0014] As a further preferred embodiment of the present invention, when there is only one exhaust port in the enclosed space, the area of ​​the exhaust port does not exceed 5% of the area of ​​the precursor wet film;

[0015] When there is a group of exhaust port arrays in the enclosed space, the area of ​​the exhaust port region formed by connecting adjacent exhaust ports does not exceed 5% of the area of ​​the precursor wet film.

[0016] As a further preferred embodiment of the present invention, there is a gap between the inner cavity side wall of the enclosed space and the precursor wet film, and the maximum spacing of the gap does not exceed 50% of the width of the precursor wet film.

[0017] As a further preferred embodiment of the present invention, when there is only one exhaust port in the enclosed space, the exhaust port is linear, circular or polygonal in shape;

[0018] When there is a group of exhaust port arrays in the enclosed space, the shapes of any two exhaust ports are the same, which are linear, circular or polygonal.

[0019] As a further preferred embodiment of the present invention, in step (1), the monovalent cation in the monovalent salt is a monovalent organic cation or an alkali metal cation; wherein the monovalent organic cation is specifically CH3NH3 + 、CH(NH2)2 + 、CH3NH2OH + 、(CH3)2NHOH + 、C(NH2)3 + 、(CH3)2NH2 + 、NH2CH2NH3 + or CH3C(NH2)2 + ; The alkali metal cation is specifically Cs + ;

[0020] The divalent metal cation in the divalent metal salt is Pb 2+ Sn 2+ ,Ge 2+ or Cu 2+ ;

[0021] The halogen ion in the halogen salt is F - , Cl - Br - or I - ; The pseudo-halogen ion in the pseudo-halogen salt is CN - or SCN - .

[0022] As a further preference of the present invention, in step (1), the solvent is an amide, a lactone, a sulfoxide or an ether alcohol.

[0023] As a further preferred embodiment of the present invention, in step (2), the coating is spin coating, blade coating, drop coating, slit coating, printing coating or inkjet coating.

[0024] As further preferred embodiment of the present invention, in step (2), the substrate is a planar substrate or a porous substrate with a porous film deposited thereon.

[0025] Through the above technical scheme conceived by the present invention, compared with the prior art, the present invention controls the volatilization position and volatilization direction of the solvent in the precursor wet film, so that the precursor wet film is locally supersaturated in a pre-selected area, and nucleation is suppressed at other positions, and while achieving localized nucleation at any position, an in-plane concentration gradient is established to achieve directional continuous growth in the plane. The obtained halide perovskite film has greatly improved crystallization quality due to localized nucleation and in-plane directional continuous growth crystallization. In the present invention, the process of localized nucleation and in-plane continuous growth of the perovskite film is controlled, so that a highly crystalline perovskite film that continues to grow after localized nucleation (i.e., after obtaining very few or even a single crystal nucleus in a pre-selected local area) can be obtained.

[0026] Taking the control of the solvent volatilization position and volatilization direction by using a confined space with a specific exhaust port design as an example, by placing the precursor wet film in a confined space and heating it, the solvent in the precursor wet film quickly evaporates to the confined space so that the solvent vapor concentration in the space reaches saturation, and the perovskite concentration in the wet film is far from the critical saturation concentration for uniform nucleation; at the same time, the solvent vapor near the exhaust port in the confined space preferentially diffuses to the external space (except for the actively set exhaust port, the other parts of the confined space are kept sealed), and the height of the confined space is controlled to limit the convective diffusion of the solvent vapor away from the exhaust port to the exhaust port; the wet film near the exhaust port is preferentially diffused because the solvent vapor in this area diffuses preferentially Dispersed to the external space, the wet film in this area preferentially reaches supersaturation, and nucleation in this area begins to occur preferentially; at the same time, since the solvent vapor near the exhaust port is removed preferentially, the wet film forms a specific concentration gradient in the direction where the solvent evaporates, and the crystal nuclei near the exhaust port begin to grow continuously in the direction opposite to the volatilization direction. The growth process at the solid-liquid interface in the perovskite film causes the decrease in supersaturation in the wet film to reach a balance with the increase in saturation brought about by solvent volatilization, and the position far away from the solid-liquid interface cannot evaporate to the external space, thereby preventing the increase in solution concentration at other positions, ensuring the directional growth of the crystal nuclei, and finally obtaining a halide perovskite film with positioned nucleation and directional continuous growth in the plane. That is to say, the present invention first suppresses the continuous volatilization of the precursor solution through the balance of saturated vapor pressure, maintains the slow growth of the concentration of the precursor solution, and then sets an exhaust port at a selected position so that the solvent vapor in this area can evaporate normally to the external space, thereby making the concentration of the selected area higher than that of other positions, so that nucleation can be achieved at the selected position.

[0027] In addition to the above analysis of how to make the concentration reach supersaturation at the selected position and nucleate first, after nucleation, how to establish a concentration gradient in the plane so that the nucleation point in the region can continue to grow, and how to suppress the nucleation at other positions during the growth of perovskite so that the perovskite can continue to grow to the end, these two aspects are also what the present invention needs to consider in order to achieve better technical effects. To this end, the present invention sets the distance between the upper surface of the precursor wet film and the top surface of the inner cavity of the enclosed space to an extremely narrow thickness. For example, the height distance between the top surface of the inner cavity of the enclosed space and the upper surface of the precursor wet film can be preferably less than 5% of the length of the precursor wet film. Such a narrow space combined with the design of the exhaust port can first realize the directional volatilization of solvent vapor toward the exhaust port to the external space, thereby realizing the establishment of a horizontal concentration gradient in the plane; second, the narrow space will cause the solvent vapor to quickly fill the space to reach the saturated vapor pressure, so that the solvent vapor away from the exhaust port cannot further volatilize, thereby suppressing the nucleation at other positions. If the distance between the precursor wet film and the top of the confined space is too large, it will often lead to excessive evaporation of solvent vapor, resulting in the appearance of new nucleation points at other locations. Of course, the top of the confined space cannot be in direct contact with the precursor wet film. Contact with the precursor wet film will cause a layer of surface tension to form between the precursor wet film and the top of the confined space. The orderly evaporation of the disordered solvent may even provide surface energy for the nucleation of perovskite, causing the perovskite to heterogeneously nucleate directly at this location.

[0028] In addition, the present invention also suppresses nucleation at other positions by preferentially controlling the distance between the inner cavity side wall of the enclosed space and the precursor wet film, so that the longest distance between the inner cavity side wall of the enclosed space and the precursor wet film does not exceed 50% of the width of the precursor wet film; the distance between the precursor wet film and the inner cavity side wall of the present invention should not be too large, because too large often leads to the enlargement of the space near the side wall, thereby increasing the amount of solvent volatilization in this area and disordering the direction of solvent volatilization, thereby leading to nucleation in other areas. Of course, the inner cavity side wall cannot directly contact the wet film. Contact with the precursor wet film will cause a layer of surface tension to form between the precursor wet film and the inner wall side wall, which may provide surface energy for perovskite nucleation, causing the perovskite to directly heterogeneously nucleate at this position, thereby failing to achieve in-plane directional growth.

[0029] In summary, the method of the present invention can achieve uniform preparation of perovskite films by controlling the nucleation and growth processes, achieves high repeatability and can be applied to large-area perovskite preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the enclosed space and the porous membrane structure in the perovskite in-plane directional crystallization method provided by the embodiment of the present invention; wherein, Figure 1(a) corresponds to the bottom-confined space (i.e., the exhaust port is located at the bottom edge of the confined space); Figure 1 (b) in the figure corresponds to the right-enclosed space (i.e., the exhaust port is located at the lower right corner of the enclosed space); Figure 1 (c) in the figure corresponds to the left-enclosed space (i.e., the exhaust port is located at the lower left corner of the enclosed space); Figure 1 (d) is a schematic diagram of the detailed structure of each enclosed space unit of the bottom-enclosed space, the right-enclosed space and the left-enclosed space; Figure 1 (e) is a detailed structural schematic diagram of the porous membrane structure placed in the bottom-enclosed space in Example 1. The porous membranes in the figure are mesoporous TiO2 / mesoporous ZrO2 / mesoporous carbon from bottom to top, and the perovskite solution marked with green color is dripped in it.

[0031] Figure 2 is a cross-sectional SEM image of a porous membrane before and after in-plane directional crystal growth in an embodiment of the present invention; wherein, Figure 2 (a) in the figure corresponds to the cross section of the porous membrane before the in-plane directional crystal growth (the porous membrane is full of holes). Figure 2 (b) corresponds to the in-plane directional crystal growth (using bottom-confined space, it can be seen that after the directional crystal growth of the perovskite material, the porous membrane has been filled with perovskite).

[0032] Figure 3 It is a comparison diagram of the in-plane oriented crystallization product obtained by growth using bottom-confined space, right-confined space and left-confined space provided by an embodiment of the present invention and the crystallization product obtained by traditional non-oriented growth.

[0033] Figure 4 It is a bottom-up growth process change diagram of the halide perovskite film prepared in Example 2 of the present invention, an X-ray diffraction spectrum of the prepared perovskite film, and a synchrotron radiation X-ray diffraction result; wherein, Figure 4 (a) in the figure corresponds to the growth process change diagram, Figure 4 (b) in the figure corresponds to the X-ray diffraction pattern. Figure 4 (c) corresponds to the synchrotron X-ray diffraction result (and, Figure 4 (c) in the figure refers to the non-directional growth sample and the directional growth sample obtained in Example 2 from left to right).

[0034] Figure 5 This is a diagram showing the growth process of the halide perovskite film prepared in Example 3 of the present invention from the lower left corner to the upper right corner.

[0035] Figure 6 This is a diagram showing the growth process of the halide perovskite film prepared in Example 4 of the present invention from the lower right corner to the upper left corner.

[0036] Figure 7This is the preparation of a large-area perovskite film with a size of 10 cm×10 cm prepared in Example 5 of the present invention.

[0037] Figure 8 These are the film samples obtained during the intermediate process of Comparative Example 1 and the film samples finally prepared.

[0038] Fig. 9 This is a sample in which perovskite exists on the carbon layer surface of the thin film sample finally obtained in Comparative Example 2.

[0039] Fig.10 These are the film samples obtained during the intermediate process of Comparative Example 3 and the film samples finally prepared. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0041] Halide perovskites include ABX3 halide perovskites and their derivatives. The A position in the ABX3 halide perovskites or their derivatives is a positive monovalent cation selected from methylamine cation CH3NH3+, formamidine cation CH(NH2)2 + , Cesium cation Cs + 、Methylhydroxylamine cation CH3NH2OH + 、Dimethylhydroxylamine cation (CH3)2NHOH + 、Guanidine cation C(NH2)3 + 、Dimethylamine cation (CH3)2NH2 + 、Methylenediamine cation NH2CH2NH3 + 、acetamidine cation CH3C(NH2)2 + One or more of; B position is a positive divalent cation selected from lead Pb 2+ , Tin 2+ ,Ge 2+ 、Copper 2+ One or more of; X is a negative monovalent anion, which can be selected from fluoride ion F - 、Chloride ion Cl - 、Br - 、Iodide ion I - and pseudohalogen ions CN - 、SCN - One or more of .

[0042] Similar to the prior art CN113788629A, the perovskite precursor used to form the perovskite wet film in the present invention can first be subjected to precursor regulation, for example, it can include regulating the solvent used for the halide perovskite precursor and the solubilization treatment; the solvent is used to dissolve the halide perovskite solute to tend to a true solution, for example, it can be selected from nitrogen-methylformamide; the solubilization treatment is used to further promote the dissolution of the halide perovskite in the solvent into a true solution, including heating, stirring, ultrasound and introduction of additives; wet film coating is achieved by spin coating, scraping, drip coating, slit coating, printing, inkjet and the like; the substrate includes a planar substrate and a porous substrate with a porous film deposited thereon.

[0043] The following are specific embodiments:

[0044] Example 1

[0045] like Figure 1 As shown, three confined spaces are designed, the size of any confined space is 100mm×25mm×3mm (corresponding to length×width×height, respectively), and 5 independent closed cavities are arranged in each confined space, each of which is separated by a distance of 10mm. The wet film thickness is preset to 0.04mm, and the inner cavity size of the confined space is set to 21mm×10mm×0.24mm (corresponding to length×width×distance from the top surface of the inner cavity to the base, the same below), so that the distance between the upper surface of the wet film and the top surface of the inner cavity is 0.2mm. An exhaust port of 10mm×0.2mm (corresponding to the width×height of the exhaust port, the same below), 2mm×0.2mm, and 2mm×0.2mm are designed on the bottom, left oblique side, and right oblique side of the three confined spaces, respectively. The confined spaces designed with exhaust ports on the bottom, left oblique side, and right oblique side are named bottom-confined space, left-confined space, and right-confined space (respectively as Figure 1 As shown in (a), (b), and (c) in the figure). Due to the use of a specific exhaust port, when the precursor wet film is placed in a closed space and heated (the wet film width is 7 mm, and the distance between the wet film and the side wall is 1.5 mm, the same below), the solvent in the perovskite precursor quickly evaporates to the space, so that the space reaches the saturated vapor pressure in a very short time, and the solvent volatilization in the wet film is suppressed; at the same time, the solvent vapor near the exhaust port diffuses from the exhaust port to the external space, and the solvent vapor volatilized from the precursor solution in this area and the solvent vapor that has evaporated to the outside of the film near the area are quickly replenished to the area, and the solvent volatilization direction is controlled from away from the exhaust port to the exhaust port, thereby forming a specific concentration gradient; the wet film solvent near the exhaust port evaporates first, and the perovskite solution in this area gradually reaches supersaturation, and nucleation occurs first. In the process of solvent volatilization, the crystal nucleus gradually grows continuously in the plane along the direction of the concentration gradient, and a halide perovskite film with localized nucleation and directional continuous growth in the plane is prepared.

[0046] A FTO conductive glass substrate with a size of 100 mm × 25 mm × 3 mm (corresponding to length × width × height, the same below) was heated to 450°C on a hot stage, and a dense titanium dioxide layer was prepared by spray pyrolysis of diisopropoxy diacetylacetonate titanium; after the substrate was cooled, an 800 nm titanium dioxide layer was deposited by screen printing, and annealed at 500°C for 40 min to form a porous membrane; after the substrate was cooled, a 2 μm zirconium oxide layer was deposited by screen printing and dried at 70°C; after the zirconium oxide was dried, a 30 μm carbon layer was deposited thereon by screen printing, and annealed at 400°C for 30 min to prepare a three-layer porous membrane skeleton; in this way, 5 three-layer porous membrane regions will be formed on each FTO substrate, and each porous membrane region is separated by 13 mm (the same below, such as Figure 1 (e) in the figure); weigh 1mmol lead iodide PbI2, 1mmol methylamine iodide MAI, add 1mL nitrogen-methylformamide (ie, N-methylformamide) solvent, 0.15mmol methylamine chloride MACl additive, heat and stir at 60°C for 1h, then put in an oven for aging for 20h to obtain a perovskite precursor solution; drop the perovskite precursor solution on the three-layer porous membrane skeleton to obtain a porous wet membrane, cover the bottom-enclosed space, left-enclosed space, and right-enclosed space on the FTO substrate, so that the porous membrane substrate can be completely in the inner cavity of each enclosed space, and realize the crystallization of perovskite in the porous membrane (specific parameters are shown in Table 1). Scanning electron microscopy was used to observe that the filling of perovskite in the porous membrane was good (such as Figure 2 As shown). In order to compare the difference between positioned nucleation and non-positioned nucleation, a substrate was placed in a non-directional growth-confined space with an inner cavity size of 110mm×30mm×6mm, and heated on a 56°C hot plate. During the crystallization process, the substrate filled with perovskite was observed. In the bottom-confined space, a small amount of crystallization area appeared near the bottom exhaust port, while other positions were still in a solution state; in the left-confined space, a small amount of crystallization area appeared near the left hypotenuse exhaust port, while other positions were still in a solution state; in the right-confined space, a small amount of crystallization area appeared near the right hypotenuse exhaust port, while other positions were still in a solution state; in the non-directional growth-confined space, crystallization areas appeared at random positions. After the growth of perovskite in the porous membrane was completed, the crystallization conditions of four cases were observed, among which the bottom-confined space, right-confined space, and left-confined space grew densely without interfaces (as shown in Figure 2). Figure 3 Non-directional growth - in a confined space, growth has a clear interface (same as Figure 3 shown).

[0047] Table 1

[0048]

[0049] Example 2

[0050] A FTO conductive glass substrate with a size of 100 mm × 25 mm × 3 mm (corresponding to length × width × height, the same below) was heated to 450°C on a hot stage, and a dense titanium dioxide layer was prepared by spray pyrolysis of diisopropoxy diacetylacetonate titanium; after the substrate was cooled, an 800 nm titanium dioxide layer was deposited by screen printing, and annealed at 500°C for 40 min to form a porous membrane; after the substrate was cooled, a 2 μm zirconium oxide layer was deposited by screen printing and dried at 70°C; after the zirconium oxide was dried, a 30 μm carbon layer was deposited thereon by screen printing, and annealed at 400°C for 30 min to prepare a three-layer porous membrane skeleton; in this way, five three-layer porous membrane regions will be formed on each FTO substrate, and each porous membrane region will have a spacing of 100 μm and 100 μm. 13mm apart (the same below); weigh 1mmol lead iodide PbI2, 1mmol methylamine iodide MAI, add 1mL nitrogen-methylformamide (i.e., N-methylformamide) solvent, 0.15mmol methylamine chloride MACl additive, heat and stir at 60°C for 1h, then put into an oven for aging for 20h to obtain a perovskite precursor solution; drop the perovskite precursor solution on the three-layer porous membrane skeleton to obtain a porous wet film, cover the bottom-enclosed space on the FTO substrate, so that the porous wet film can be completely in the inner cavity of each enclosed space (the distance between the porous wet film and the side wall is 1.5mm, and the distance between the upper surface of the porous wet film and the top surface of the inner cavity is 0.2mm), heat on a 56°C hot plate to achieve crystallization of perovskite in the porous membrane. During the crystallization process, the substrate filled with perovskite was observed. First, a small amount of crystallization was observed in the three-layer film area near the exhaust port on the substrate. Then, the crystallization area gradually became flat and the solid-liquid interface became stable. Then, the solid-liquid interface steadily grew away from the exhaust port. Finally, the solid-liquid interface advanced to the entire area, ending the growth (e.g. Figure 4 The obtained perovskite was subjected to an X-ray diffraction pattern and compared with the perovskite obtained in a non-directional growth-enclosed space. The test results are shown in FIG. Figure 4 As shown in (b), the crystal quality of the perovskite placed in the bottom-confined space is much higher than that in the non-directional growth-confined space. At the same time, they were characterized by synchrotron radiation X-ray diffraction. The test results are as follows Figure 4 As shown in (c), it can be seen that the perovskite obtained by bottom-confined space shows a high degree of orientation, while the perovskite obtained by non-directional growth-confined space has no obvious orientation, which is also consistent with the results of X-ray diffraction. This shows that the method can achieve the controllable preparation of high-quality halide perovskite films with localized nucleation, continuous growth in the plane and high orientation.

[0051] Example 3

[0052] A FTO conductive glass substrate with a size of 100 mm × 25 mm × 3 mm (corresponding to length × width × height, the same below) was heated to 450°C on a hot stage, and a dense titanium dioxide layer was prepared by spray pyrolysis of diisopropoxy diacetylacetonate titanium; after the substrate was cooled, an 800 nm titanium dioxide layer was deposited by screen printing, and annealed at 500°C for 40 min to form a porous membrane; after the substrate was cooled, a 2 μm zirconium oxide layer was deposited by screen printing and dried at 70°C; after the zirconium oxide was dried, a 30 μm carbon layer was deposited thereon by screen printing, and annealed at 400°C for 30 min to prepare a three-layer porous membrane skeleton; in this way, five three-layer porous membrane regions will be formed on each FTO substrate, and each porous membrane region will have a spacing of 100 μm and 100 μm. 13mm apart (the same below); weigh 1mmol lead iodide PbI2, 1mmol methylamine iodide MAI, add 1mL nitrogen-methylformamide (i.e., N-methylformamide) solvent, 0.15mmol methylamine chloride MACl additive, heat and stir at 60°C for 1h, then put into an oven for aging for 20h to obtain a perovskite precursor solution; drop the perovskite precursor solution on the three-layer porous membrane skeleton to obtain a porous wet film, cover the left-closed space on the FTO substrate, so that the porous wet film can be completely in the inner cavity of each closed space (the distance between the porous wet film and the side wall is 1.5mm, and the distance between the upper surface of the porous wet film and the top surface of the inner cavity is 0.2mm), heat on a 56°C hot plate to achieve crystallization of perovskite in the porous membrane. During the crystallization process, the substrate filled with perovskite was observed. As the solvent continued to evaporate, a small amount of crystallization was observed in the lower left corner of the three-layer film area on the substrate near the exhaust port. Subsequently, the crystallization area gradually became flat and the solid-liquid interface became stable. Then, the solid-liquid interface steadily grew toward the upper right, away from the exhaust port. Finally, the solid-liquid interface advanced to the entire area, ending the growth (e.g. Figure 5 shown).

[0053] Example 4

[0054] A FTO conductive glass substrate with a size of 100 mm × 25 mm × 3 mm (corresponding to length × width × height, the same below) was heated to 450°C on a hot stage, and a dense titanium dioxide layer was prepared by spray pyrolysis of diisopropoxy diacetylacetonate titanium; after the substrate was cooled, an 800 nm titanium dioxide layer was deposited by screen printing, and annealed at 500°C for 40 min to form a porous membrane; after the substrate was cooled, a 2 μm zirconium oxide layer was deposited by screen printing and dried at 70°C; after the zirconium oxide was dried, a 30 μm carbon layer was deposited thereon by screen printing, and annealed at 400°C for 30 min to prepare a three-layer porous membrane skeleton; in this way, five three-layer porous membrane regions will be formed on each FTO substrate, and each porous membrane region will have a spacing of 100 μm and 100 μm. 13mm apart (the same below); weigh 1mmol lead iodide PbI2, 1mmol methylamine iodide MAI, add 1mL nitrogen-methylformamide (i.e., N-methylformamide) solvent, 0.15mmol methylamine chloride MACl additive, heat and stir at 60°C for 1h, then put into an oven for aging for 20h to obtain a perovskite precursor solution; drop the perovskite precursor solution on the three-layer porous membrane skeleton to obtain a porous wet film, cover the right-enclosed space on the FTO substrate, so that the porous wet film can be completely in the inner cavity of each enclosed space (the distance between the porous wet film and the side wall is 1.5mm, and the distance between the upper surface of the porous wet film and the top surface of the inner cavity is 0.2mm), heat on a 56°C hot plate to achieve crystallization of perovskite in the porous membrane. During the crystallization process, the substrate filled with perovskite was observed. As the solvent continued to evaporate, a small amount of crystallization was observed in the lower right corner of the three-layer film area on the substrate near the exhaust port. Subsequently, the crystallization area gradually became flat and the solid-liquid interface became stable. Then, the solid-liquid interface steadily grew toward the upper left, away from the exhaust port. Finally, the solid-liquid interface advanced to the entire area, ending the growth (e.g. Figure 6 shown).

[0055] Example 5

[0056] A porous membrane substrate with a size of 10 cm×10 cm (length×width) was deposited on a FTO substrate, 1 mmol of lead iodide PbI2 and 1 mmol of methylamine iodide MAI were weighed, 1 mL of nitrogen-methylformamide solvent and 0.15 mmol of methylamine chloride MACl additive were added thereto, and the mixture was heated and stirred at 60°C for 1 hour and then aged in an oven for 20 hours to obtain a perovskite precursor solution; the perovskite precursor solution was drop-coated on a three-layer porous membrane skeleton to obtain a porous wet membrane (the three-layer porous membrane skeleton is similar to that in Example 1, and is, from bottom to top, 800 nm of dielectric The porous wet film was placed in a closed space with an inner cavity size of 10.3 cm × 10.2 cm × 0.24 mm (corresponding to the bottom side length × the side side length × the distance between the top surface of the inner cavity and the substrate) (the distance between the porous wet film and the side wall was 1.5 mm, and the distance between the upper surface of the porous wet film and the top surface of the inner cavity was 0.2 mm). An array of 10 exhaust ports was set at the exhaust port, each of which was 1 cm × 0.2 mm (width × height), and the interval between each exhaust port was set to a distance of a scale line ( Figure 7 The 10 exhaust ports are arranged as an array with a total length of 10 cm, so that the porous wet film can be completely in the inner cavity and heated on a hot stage to achieve the crystallization of perovskite in a large area of ​​10 cm × 10 cm porous film (such as Figure 7 As shown, the engraved lines in the figure are the module design in a 10cm×10cm large area battery).

[0057] Comparative Example 1:

[0058] A bottom-enclosed space is redesigned. The enclosed space is basically the same as the bottom-enclosed space in Example 1, except that the inner cavity size of the enclosed space is changed to 21mm×10mm×1.12mm (corresponding to length×width×the distance between the top surface of the inner cavity and the substrate), so that the distance between the upper surface of the porous wet film and the top surface of the inner cavity is greater than 1mm. The composition and size of the wet film are the same as in Example 1, and the other conditions are basically the same as in Example 2. Heating on a 56°C hot plate allows the crystallization of perovskite in the porous film. During the crystallization process, the substrate filled with perovskite is observed. As the solvent continues to evaporate, the perovskite solid-liquid interface can steadily advance and grow in a direction away from the exhaust port at the beginning. However, as the advancement continues, the distance between the upper surface of the wet film and the top surface of the inner cavity is too high, resulting in the appearance of new nucleation sites at other locations, thereby forming the growth of multiple crystal nuclei and producing interfaces, such as Figure 8 .

[0059] Comparative Example 2:

[0060] A bottom-enclosed space is redesigned. The enclosed space is basically the same as the bottom-enclosed space in Example 1, except that the inner cavity size of the enclosed space is changed to 21mm×10mm×0.04mm (corresponding to length×width×the distance between the top surface of the inner cavity and the substrate), and the exhaust port size is changed to 10mm×0.04mm (corresponding to exhaust port width×height), so that the distance between the upper surface of the porous wet film and the top surface of the inner cavity is 0mm (at this time, the perovskite solution will be in contact with the top surface of the inner cavity). The composition and size of the wet film are the same as in Example 1, and the other conditions are basically the same as in Example 2. Heating on a 56°C hot plate allows the crystallization of perovskite in the porous film. During the crystallization process, the substrate filled with perovskite is observed. As the solvent continues to evaporate, the upper surface of the wet film is in direct contact with the top surface of the inner cavity, causing the perovskite to nucleate directly in the topmost carbon layer, such as Fig. 9 .

[0061] Comparative Example 3:

[0062] A bottom-enclosed space is redesigned. The enclosed space is basically the same as the bottom-enclosed space in Example 1, except that the inner cavity size of the enclosed space is changed to 21mm×17mm×0.24mm (corresponding to length×width×the distance between the top surface of the inner cavity and the substrate). Each enclosed cavity is separated by a distance of 3mm, so that the distance between the porous wet film and the side wall is 5mm. The composition and size of the wet film are the same as in Example 1, and the other conditions are basically the same as in Example 2. Heating on a 56°C hot plate allows the crystallization of perovskite in the porous membrane. During the crystallization process, the substrate filled with perovskite is observed. As the solvent continues to evaporate, the perovskite solid-liquid interface can steadily advance and grow in a direction away from the exhaust port at the beginning. However, as the advancement continues, the distance between the side wall and the wet film is too large, and the spatial range of the enclosed space becomes larger, resulting in the appearance of new nucleation sites at other locations, thereby forming the growth of multiple crystal nuclei and producing interfaces, such as Fig.10 .

[0063] The above embodiments are only examples. For example, the specific position of the exhaust port in the enclosed space can be pre-selected as needed, and can be located on the top surface or on the side wall; the shape and size of the exhaust port can be preferably adjusted, and can be a single setting for the preparation of a small-area film, or an array setting for the preparation of a large-area film (for example, the size of the exhaust port can be determined based on the size of the generated film area, preferably not more than 5% of the precursor wet film area, so as to effectively control the volatilization rate of the solvent, so that the volatilization position and volatilization direction of the solvent can be controlled more effectively to control the positioning nucleation and the directional growth in the plane). The setting position of the exhaust port is pre-set as needed. For a certain enclosed space, its exhaust port can be either a single exhaust port or a group of exhaust port arrays; for the exhaust port array, the exhaust port array can be used for the preparation of a small-area film, or can be arranged in an array for the preparation of a large-area film. For this group of exhaust port arrays, the shortest distance between the edges of two adjacent exhaust ports does not exceed 20 mm, so that this group of exhaust port arrays will be able to correspond to a whole exhaust port area.

[0064] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for in-plane directional crystallization of halide perovskite, characterized in that: The following steps are involved: (1) adding a monovalent salt and a divalent metal salt to a solvent to obtain a perovskite precursor; the monovalent salt and the divalent metal salt are both halogen salts or pseudo-halogen salts; (2) coating the perovskite precursor obtained in step (1) on a substrate to obtain a precursor wet film; (3) By regulating the evaporation position and evaporation direction of the solvent in the precursor wet film, the precursor wet film is controlled to be preferentially supersaturated in a single selected local area, so as to achieve localized nucleation at a controllable position, while inhibiting the nucleation at other positions, establishing a radial in-plane concentration gradient, and achieving directional continuous growth in the plane, thereby obtaining a halide perovskite film with localized nucleation and continuous growth; In step (3), the volatilization position and volatilization direction of the solvent in the precursor wet film are regulated, specifically: The precursor wet film is placed in a closed space for heating, the precursor wet film only contacts the substrate located below, and does not contact the inner cavity side wall and top surface of the closed space; the closed space has only one single exhaust port at a pre-selected position, or a group of exhaust port arrays; and for this group of exhaust port arrays, the shortest distance between the edges of two adjacent exhaust ports does not exceed 20 mm, so that this group of exhaust port arrays can correspond to a whole exhaust port area; Due to the setting of the exhaust port, the saturated vapor generated by the heating of the precursor wet film in the confined space will be discharged from the exhaust port first, so that the wet film area corresponding to the exhaust port will reach supersaturation first and position nucleation will occur; at the same time, a radial solvent vapor gradient pointing to the exhaust port will be formed in the confined space, so that a radial in-plane concentration gradient will also be formed in the wet film surface, thereby realizing the radial directional continuous growth of halide perovskite in the surface.

2. The method according to claim 1, characterized in that: There is a gap between the inner cavity top surface of the enclosed space and the upper surface of the precursor wet film, and the spacing of the gap is less than 5% of the length of the precursor wet film in the directional growth direction.

3. The method according to claim 1, characterized in that: When there is only one exhaust port in the enclosed space, the area of ​​the exhaust port does not exceed 5% of the area of ​​the precursor wet film; When there is a group of exhaust port arrays in the enclosed space, the area of ​​the exhaust port region formed by connecting adjacent exhaust ports does not exceed 5% of the area of ​​the precursor wet film.

4. The method according to claim 1, characterized in that: There is a gap between the inner cavity side wall of the enclosed space and the precursor wet film, and the maximum spacing of the gap does not exceed 50% of the width of the precursor wet film.

5. The method according to claim 1, characterized in that: When there is only one exhaust port in the enclosed space, the exhaust port is linear, circular or polygonal in shape; When there is a group of exhaust port arrays in the enclosed space, the shapes of any two exhaust ports are the same, which are linear, circular or polygonal.

6. The method according to claim 1, characterized in that: In step (1), the monovalent cation in the monovalent salt is a monovalent organic cation or an alkali metal cation; wherein the monovalent organic cation is specifically CH3NH3 + 、CH(NH2)2 + 、CH3NH2OH + 、(CH3)2NHOH + 、C(NH2)3 + 、(CH3)2NH2 + 、NH2CH2NH3 + or CH3C(NH2)2 + The alkali metal cation is specifically Cs + ; The divalent metal cation in the divalent metal salt is Pb 2+ Sn 2+ ,Ge 2+ Cu 2+ ; The halogen ions in the halogen salt are F-, Cl - Br - or I-; the pseudo-halogen ion in the pseudo-halogen salt is CN - or SCN-.

7. The method according to claim 1, characterized in that: In step (1), the solvent is an amide, a lactone, a sulfoxide or an ether alcohol.

8. The method according to claim 1, characterized in that: In step (2), the coating is spin coating, blade coating, drop coating, slit coating, printing coating or inkjet coating.

9. The method according to claim 1, characterized in that: In step (2), the substrate is a planar substrate or a porous substrate with a porous film deposited thereon.

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