Device for preparing large-size perovskite single crystal or multi-wafer

Abstract

The invention discloses a device for preparing a large-size perovskite single crystal or multi-wafer, the device uses a temperature control unit to regulate and control the temperature of different heating units so as to form a temperature difference, and further induce the formation of a crystal nucleus at a high-temperature end or a low-temperature end, because the temperature of the heating units can be regulated and controlled, the size and the position of the temperature difference can be regulated and controlled, and the large-size perovskite single crystal or multi-wafer can be prepared. Therefore, the nucleation position of the induced crystal can be flexibly and accurately positioned based on the size and position of the temperature difference, and compared with natural nucleation, the nucleation speed is higher. When a crystal nucleus is formed in a target area and a crystal growth stage is entered, the temperature of each heating unit can be adjusted, and the temperature gradient of an area without crystals can be maintained or flexibly adjusted on the basis of crystal expansion requirements, so that the front edge of the crystals is kept in a moderate supersaturated state, and the crystal growth speed is increased.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of material science and new energy, and particularly relates to a device for preparing large-size perovskite single crystal / multicrystal wafer. BACKGROUND

[0002] Perovskite materials have been widely used in photovoltaic devices such as solar cells, photodetectors and light-emitting diodes due to their excellent optoelectronic properties and low-cost preparation process. Compared with perovskite polycrystalline thin films, perovskite single crystals have lower defect density (10 8 -10 10 cm -3 vs10 17 -10 19 cm -3 ), higher carrier mobility (10-10 2 cm 2 V - 1 s -1 ), wider absorption spectrum and higher material stability, and exhibit more excellent performance and stability in photovoltaic devices.

[0003] However, the growth of perovskite single crystals is time-consuming and the shape is often not suitable for device preparation. In view of this, documents Adv. Opt. Mater. 2016, 4, 1829; Sci. China Chem. 2017, 60, 1367 report that a large-size single crystal (~10 cm) can be obtained first, and then the single crystal wafer suitable for device preparation can be processed by wire cutting and other methods. However, this process is very challenging and the material loss is large, and an additional polishing process is required.

[0004] The space confinement method opens up a new path for the preparation of high-quality single crystal wafers due to its unique physical constraint environment. In the micron-sized gap, the ion transport of the precursor is hindered, and the extremely low transport efficiency is like a huge obstacle in the way of ideal crystallization. Although the introduction of a dynamic flow microreactor system can accelerate the diffusion and migration of ions to some extent and improve the transport efficiency, it is still difficult to overcome the problem that the nucleation center is difficult to control accurately. In this micron-sized microscopic world, the nucleation process is subtly affected by many factors, such as the slight disturbance of the fluid and the local fluctuation of the ion concentration, which will cause the number and distribution of the nucleation center to be unpredictable. This makes it difficult to guarantee the uniformity and consistency of the crystal when growing a single crystal wafer, and problems such as polycrystalline mixture and crystal defects are likely to occur, which greatly limits the further application of the space confinement method in the large-scale preparation of high-quality single crystal wafers. At present, the size of the single crystal wafer reported in the document Adv. Mater. 2016, 28, 9204 is about 1 cm.

[0005] In another aspect, due to the high defect tolerance of perovskite, it is reported in Nat. Phot. 2017, 11, 436 that perovskite polycrystalline sheet can also be quickly prepared by the method of pressing sheet for optoelectronic devices, especially for X-ray detection imaging which has been reported more. However, the perovskite material is relatively brittle, and the processing technology is strict, and the defect density of the polycrystalline sheet prepared by this method is usually high, and the mobility is in the order of 10 -1 cm 2 V -1 s -1 magnitude, which has a large gap with single crystal sheet, affecting the performance and stability of the prepared device.

[0006] Therefore, it is urgent to develop a device for quickly preparing large-area high-quality perovskite single crystal / polycrystalline sheet, so as to facilitate the application of perovskite in high-performance and high-stability optoelectronic devices. SUMMARY

[0007] The present application provides a device for preparing large-size perovskite single crystal or polycrystalline sheet, which can quickly prepare large-size perovskite single crystal or polycrystalline sheet with good quality.

[0008] The present application provides a device for preparing large-size perovskite single crystal or polycrystalline sheet, which comprises:

[0009] A perovskite single crystal or polycrystalline growth system, wherein the inside or bottom of the perovskite single crystal or polycrystalline growth system is provided with a heating plate, and the heating plate is composed of a plurality of heating units arranged in an array;

[0010] A precursor solution circulation system connected with the perovskite single crystal or polycrystalline growth system, for circulating perovskite precursor solution with the perovskite single crystal or polycrystalline growth system;

[0011] A temperature control system connected with the heating unit, for controlling the temperature of the heating unit in the nucleation induction stage to form a target temperature difference between the heating units so as to induce nucleation, for maintaining or expanding the temperature difference in the crystal growth stage in the region where no crystal appears, so as to maintain the crystal front in a supersaturated state and realize crystal growth, and for adjusting the temperature of the heating unit after obtaining a perovskite single crystal or polycrystalline sheet of target size, so that the temperature of the heating plate drops to room temperature.

[0012] Preferably, in the nucleation induction stage, the temperature control system controls the temperature of the heating unit to reach the target temperature difference within 6-12h. The present application avoids the formation of too many small crystal nuclei caused by too fast instantaneous supersaturation, thereby reducing the quality of the crystal.

[0013] Preferably, in the induction nucleation stage, the temperature control system controls the temperature of the heating unit so that the temperature of the middle region of the heating plate and the temperature of the two end regions form a target temperature difference.

[0014] Preferably, after obtaining the perovskite single crystal or polycrystalline wafer of target size, the temperature control system adjusts the temperature of the heating unit so that the heating plate is cooled to room temperature within 1-2h, while the precursor solution circulation system stops providing the perovskite precursor solution to the perovskite single crystal or polycrystalline growth system.

[0015] The present application controls the cooling rate of the heating plate and gradually reduces the temperature of each region of the heating plate to room temperature, and the process is preferably slow to avoid cracking of the crystal due to thermal stress, while stopping or reducing the speed of circulation to prevent supercooling from generating new unnecessary crystal nuclei.

[0016] Preferably, the surface of the heating plate is coated with a polytetrafluoroethylene hydrophobic material. The wafer should be easily separated from the plate; if there is slight adhesion, a piece of inert material (such as a PTFE sheet) can be used to gently pry up a corner of the wafer. The hydrophobic surface of the heating plate reduces the formation of heterogeneous nucleation centers and stress concentration points, and the wafer tends to grow in a single orientation with fewer internal defects. At the same time, the low-temperature process avoids decomposition of the organic components at high temperatures, improving the stability of the crystal.

[0017] Preferably, the width of each heating unit is 1-10mm and the length is 10-500mm.

[0018] Preferably, the precursor solution circulation system further comprises a gasket and a cover plate;

[0019] The gasket is located between the heating plate and the cover plate, and the gasket is arranged at the edge of the heating plate, with gaps between the gaskets. The precursor solution circulation system can provide and receive the perovskite precursor solution through the gaps, and the gasket is used to adjust the distance between the heating plate and the cover plate.

[0020] The cover plate is used to limit the growth direction of the perovskite single crystal or polycrystalline, so that the perovskite single crystal or polycrystalline grows laterally.

[0021] Preferably, the gasket can also be a sealing ring gasket, which can form a closed space with the cover plate and the heating plate, and the precursor solution circulation system provides and receives the perovskite precursor solution to the closed space through the sealing ring gasket, realizing the circulation of the perovskite precursor solution.

[0022] The application strictly limits the height of the growth space by using replaceable gaskets, so that the thickness of the obtained perovskite wafer is basically determined by the thickness of the gasket, avoiding the problem of uncontrolled thickening of the crystal. The upper and lower surfaces of the wafer are parallel and smooth, and the single crystal wafer material with the required thickness can be obtained without subsequent mechanical slicing, reducing processing damage.

[0023] Preferably, the precursor solution circulation system comprises:

[0024] A solution storage container for storing the saturated perovskite precursor solution; preferably kept at a constant temperature to maintain a stable saturated concentration;

[0025] An infusion pump, an inlet pipe and an outlet pipe, one end of the inlet pipe and the outlet pipe being connected with the precursor solution circulation system, and the other end being connected with the solution storage container, the perovskite precursor solution in the solution storage container is introduced into the perovskite single crystal or polycrystal growth system through the inlet pipe by the infusion pump, and the perovskite precursor solution in the perovskite single crystal or polycrystal growth system is recovered into the solution storage container through the outlet pipe, realizing circulation flow;

[0026] A flow control device connected with the infusion pump for adjusting the circulation speed of the perovskite precursor solution, or automatically supplementing the perovskite precursor solution to the perovskite single crystal or polycrystal growth system after detecting that the concentration of the perovskite precursor solution in the perovskite single crystal or polycrystal growth system decreases to a set value.

[0027] The flow control device provided by the application comprises a valve and a flow controller. The precursor solution circulation system provided by the application realizes the circulation flow of the perovskite precursor solution.

[0028] Preferably, the perovskite precursor solution refers to MAPbI3, MAPbBr3, MAPbCl3, FAPbI3, FAPbBr3, FAPbCl3, CsPbI3, CsPbBr3, CsPbCl3, and a blended precursor solution therebetween.

[0029] The application also provides a use method of the device for preparing large-size perovskite single crystal or polycrystal wafer, comprising:

[0030] Device preparation: clean and dry the surface of the heating plate. Select a gasket of appropriate thickness and place it on the periphery of the heating plate surface at a predetermined position. Place the cover plate on it and align the gasket position, use clamps, screws or fasteners to fix the cover plate and the heating plate, so as to form a uniform gap cavity therebetween. If a closed environment is required, a circle of sealing silicone can be pre-coated on the contact surface of the gasket and the plate. Ensure that the inlet and outlet are connected to the solution circulation system. The whole device can be operated in an inert atmosphere box to prevent the influence of environmental humidity.

[0031] Solution injection: A saturated solution of perovskite precursors (e.g. organic-inorganic halide perovskite precursors dissolved in an organic solvent until reaching room temperature saturation concentration) is prepared. The saturated solution is slowly injected into the gap between the hot plate and the cover plate through the inlet of the solution circulation system until the growth cavity is filled and no air bubbles remain. If open growth is employed (i.e. not completely sealed), the entire hot plate (with cover plate and gasket assembled) can be immersed in a container holding the saturated precursor solution, allowing the gap to communicate with the external solution through the edges, thus utilizing the external solution as the supply source. After the injection is complete, the solution circulation pump is started to slowly circulate the flow within the gap, or in the case of open conditions, to ensure sufficient convection of the solution in the external container to avoid local depletion of solute.

[0032] Temperature gradient induced nucleation: The temperature control system is activated to heat (or cool) the individual zones of the hot plate to target temperatures according to a pre-determined scheme. For example, in one preferred scheme, the middle region of the hot plate is set to a temperature T1 (e.g. 50°C) and the ends are set to a temperature T2 (e.g. 60°C), creating a temperature difference ΔΤ. In some embodiments, this corresponds to inverse temperature crystallization conditions: the solution solubility decreases at the high temperature end, and supersaturation and thus nucleation is induced first at the high temperature end. Alternatively, temperature induced crystallization can be employed, with nucleation occurring first at the low temperature end, as desired. By adjusting the magnitude and location of ΔΤ, the location of the induced nucleation of the crystal can be positioned (e.g. to start nucleation at the cooler side of the hot plate). The rate of temperature increase or decrease is controlled slowly and uniformly during this stage to obtain a small and ideal initial number of crystal nuclei. For example, the target temperature gradient can be ramped up over 30 minutes to avoid too rapid nucleation of too many nuclei.

[0033] Fast growth phase: Once nucleation has occurred in the target region, the crystal growth phase is entered. The temperature gradient field is maintained or adjusted as needed for crystal expansion. For example, the temperature difference at the ends can be slightly increased or the temperature at the high temperature end can be held constant while the temperature at the low temperature end is slowly decreased to maintain a moderate supersaturation at the crystal front. The solution circulation system continues to operate, with fresh saturated solution being continuously fed to the crystal growth front to replenish the local solute concentration that is depleted by crystallization, thus greatly increasing the growth rate.

[0034] Under the optimized conditions of the present application, the crystal growth rate is significantly higher than that of conventional static methods. For example, under temperature zone conditions of about 60-70°C, a crystal thickness growth rate on the order of several microns per minute can be achieved, and the lateral expansion rate of the crystal can reach several millimeters to centimeters per day. By controlling the growth time, the final size of the wafer is limited by the growth space, which can approach the area defined by the hot plate and the cover plate (e.g. the diagonal can reach several centimeters). The growth period can last from a few hours to several tens of hours, and the appropriate end time or growth stop criterion (such as when the circulating solution concentration no longer decreases or the crystal reaches the container boundary) is selected according to the desired wafer size and solute supply.

[0035] Cooling down: After the crystal reaches the expected size and thickness, the temperature of each area of the heating plate is gradually lowered to room temperature, and the process should be slow to avoid cracking of the crystal due to thermal stress. The temperature control system can follow the preset program to cool the device smoothly within 1-2 hours. During the cooling process, the solution circulation can be stopped or changed to slow flow to prevent supercooling and generate new unnecessary crystal nuclei.

[0036] Wafer removal: After the temperature drops to ambient temperature and stabilizes, stop the solution circulation and drain or pour the remaining solution from the growth cavity. Carefully loosen the cover plate fixing device and remove the cover plate to see the completed perovskite wafer laid on the heating plate. Due to the hydrophobic treatment of the heating plate surface, the wafer should be easily separated from the plate; if there is slight adhesion, a piece of inert material (such as PTFE sheet) can be used to gently pry a corner to lift the wafer. The removed wafer is placed in an inert atmosphere to dry or the surface residual liquid is absorbed with filter paper, and after natural drying, a perovskite wafer with thickness controlled by the gasket, large area and high grain quality is obtained. For single crystal wafers, a single grain usually covers the entire area if the above steps are properly controlled; if a polycrystalline sheet is generated, the size of the large grain is also much larger than that of traditional polycrystalline film, and the overall performance is still excellent.

[0037] Compared with the prior art, the beneficial effects of the present application are:

[0038] The present application utilizes the temperature control unit to regulate the temperature of different heating units, thereby forming a temperature difference, and then inducing the formation of crystal nuclei at the high temperature end or the low temperature end. Since the temperature of the heating unit can be regulated, the size and position of the temperature difference can be regulated, thereby the present application can more flexibly and accurately locate the nucleation position of the induced crystal based on the size and position of the temperature difference. Moreover, compared with natural nucleation, the nucleation speed of the present application is faster.

[0039] When the target area forms crystal nuclei and enters the crystal growth stage, the present application can adjust the temperature of each heating unit based on the demand of crystal expansion to maintain or flexibly adjust the temperature gradient in the area where no crystal appears, so as to keep the crystal front in a moderate supersaturated state and speed up the crystal growth rate.

[0040] The present application utilizes the precursor solution circulation system to continuously send fresh saturated solution to the crystal growth front area to supplement the local solute concentration reduced due to crystallization precipitation, thereby greatly improving the growth rate. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 The schematic diagram of the device for preparing large-size perovskite single crystal or polycrystalline wafer provided for the specific embodiments of the present application. DETAILED DESCRIPTION

[0042] The device structure and the method for rapidly preparing perovskite wafer are described in further detail below by means of specific examples and in conjunction with the accompanying drawings. It should be noted that the specific conditions and parameters in the examples are only used to illustrate the present application and can be adjusted according to different perovskite material systems and application requirements without departing from the spirit of the present application.

[0043] Example 1

[0044] Device structure and preparation of single-crystal perovskite wafer:

[0045] Please refer to Figure 1 (a), (b) and (c), the device described in this example includes a square heating plate 2 with a size of 10*10 cm 2 , a thickness of 10 mm, an aluminum alloy substrate surface anodized and coated with a layer of hydrophobic fluorinated coating. Nineteen equally spaced electric heating elements are embedded in the heating plate, and nineteen temperature sensors are installed correspondingly, respectively located at positions 21 to 210 of the heating plate 2. Each heating element and sensor is connected to a temperature controller 7, which can achieve independent temperature regulation of 10 regions. Through this layout, a linear gradient temperature field can be established on the heating plate from the middle to the ends.

[0046] A frame-shaped gasket 3 is placed around the hot plate 2. In this embodiment, a PTFE rectangular gasket frame (internal cavity area of about 80*80mm) with a thickness of 0.5mm is selected. A thin layer of solvent-resistant silicone is coated on the lower surface of the gasket 3 and lightly adhered to the surface of the hot plate (1) to prevent positioning deviation and solution leakage. A piece of tempered glass cover plate 1 with an area comparable to that of the hot plate is gently placed above the gasket 3, and the cover plate is pressed tightly on the gasket through the four-corner bolt fasteners, thereby forming a closed gap cavity (height 0.5mm, length and width 80mm) between the cover plate and the hot plate. The gasket 3 has a pre-prepared notch interface on each of the opposite sides: one side of the notch is connected to a liquid inlet pipe 9, and the other side is connected to a liquid outlet pipe 8. The liquid inlet pipe 9 and the liquid outlet pipe 8 are both made of solvent-resistant hoses, serving as the input and output channels of the solution circulation system, respectively. The other end of the liquid inlet pipe 9 is connected to the bottom of the solution storage container 4, and the liquid outlet pipe 8 is connected back to the top of the storage container 4, both forming a circulation loop with the container. The container 4 is a stainless steel tank with a constant temperature jacket, and inside it is pre-installed with 500mL of saturated perovskite precursor solution with the same composition as the target crystal. In this embodiment, methylammonium lead iodide perovskite (MAPbI3) is taken as an example, and the precursor solution formula is as follows: MAI and PbI2 are dissolved in γ-butyrolactone (GBL) solvent according to a 1:1 molar ratio, heated and stirred at 60℃ to reach saturation concentration, and then cooled to room temperature for standby (this is an inverse temperature crystallization system). The storage container is kept at about 50℃ through the constant temperature jacket to ensure that the solution maintains a near-saturated state and avoids crystallization. The liquid delivery pump is installed on the liquid inlet pipe, which is a type of adjustable speed peristaltic pump, and the initial setting flow rate is about 5ml / min, which is used to drive the solution circulation during the growth process.

[0047] After the device is assembled and confirmed to be leak-free, the crystal growth operation is performed. First, the above-mentioned room temperature saturated precursor solution is slowly injected into the growth cavity through the liquid inlet pipe 9 until the solution flows out from the liquid outlet pipe 8, ensuring that the gap cavity is completely filled and there are no bubbles inside. Then, the temperature controller 7 warms up according to the preset program: start the heating elements in each region, and raise the temperature of the left and right sides 210 of the hot plate to 50℃, while maintaining the temperature of the middle 21 region at 60℃ unchanged. In this way, a temperature gradient is established in the solution between the cover plate and the hot plate, decreasing from the middle 21 region (60℃) to the two sides 210 (50℃). Since the MAPbI3-GBL system has inverse temperature dissolution characteristics, the middle with higher temperature first appears supersaturated. Intentionally controlling the same temperature in the middle allows the crystal to possibly nucleate at the middle end. The temperature rising process is carried out slowly, increasing the middle from 25℃ to 60℃ at a rate of 0.1℃ / min within 350 minutes, to avoid excessive tiny crystal nuclei caused by instantaneous supersaturation.

[0048] Soon after the temperature reaches the set value, crystal nucleation can be observed (through the transparent cover plate) in the solution near the middle zone 21 of the hot plate. At this point, the crystal growth phase is entered: the temperature field is kept constant at 60°C in the middle zone 21 and 50°C in the two end zones 20, and the solution circulation pump is turned on to maintain the solution flow. As the crystals nucleate and grow in the two end zones, the fresh solution pumped in continuously replenishes the solute consumed, allowing the crystals to continue to grow. After about 1 hour, a clear crystal sheet can be seen growing in the middle and extending horizontally to the two ends. In this example, when the crystals reach a width of about 5 mm, the temperature in zone 22 is slightly increased to 60°C, so that a slight supersaturation is formed in zone 22, prompting the crystals to continue to grow to the two sides. The temperature in zones 23 to 20 is then increased to 60°C in turn, and a complete large-size crystal is obtained. The entire growth process lasts about 36 hours, during which the crystal grows horizontally until it fills the 80 mm long cavity, and the vertical thickness is limited by the 0.5 mm gap to maintain uniformity. The solution circulation pump is maintained at a flow rate of 5 ml / min for the first 12 hours, and then gradually reduced to 2 ml / min according to the solution concentration monitoring to avoid excessive supply.

[0049] After the growth is completed, the temperature control system slowly reduces the temperature in each zone of the hot plate to 25°C, and a small amount of solution is circulated during the process to prevent impurities from precipitating from the supersaturated crystals. After 1 hour of cooling, the circulation pump is stopped and the outlet valve is opened to drain the remaining solution in the cavity. After removing the bolts and taking off the cover plate 1, a whole piece of brown-black MAPbI3 perovskite single crystal sheet can be seen covering the surface of the hot plate. The size of the crystal sheet is consistent with the growth space (about 80*80 mm), and the thickness is about 0.5 mm. The crystal is intact and free of cracks under visual observation. The crystal sheet can be easily separated from the plate surface due to the hydrophobic coating, and can be lifted by a plastic tweezer at the edge of the crystal sheet. The crystal sheet is placed on filter paper to dry the surface residue, and the target perovskite single crystal sheet is obtained. X-ray single crystal diffraction analysis proves that the crystal sheet is a single crystal structure without polycrystalline spots; optical microscopy shows that the surface is flat and no obvious grain boundaries or defects are observed. It can be seen that the device and method of the present application can obtain large-size, high-quality perovskite single crystal sheets in a short time.

[0050] Example 2

[0051] Preparation of polycrystalline large-area perovskite film:

[0052] This embodiment demonstrates the use of the method of the present invention to prepare a large-area perovskite polycrystalline film, which is suitable for the production of photovoltaic devices. The device structure is similar to that of Example 1, except that: the thickness of the gasket is selected to be 0.1mm to prepare a thinner crystal film; the size of the heating plate is expanded to a circular shape with a diameter of 150mm to correspond to the size of the large-area substrate of the photovoltaic cell; and the cover plate is made of quartz glass to take into account both transparent observation and temperature resistance. The solution selected is the formamidinium lead iodide (FAPbI3) system. Its solution in γ-butyrolactone does not have the inversion temperature characteristic, so a cooling crystallization mode is adopted. Initially, the entire heating plate is heated to near the boiling point of the solvent (for example, 110°C) to make the solution completely clear, and then the temperature is slowly lowered on one side to induce nucleation.

[0053] In the specific process, a 0.1 mm thick silicone gasket 3 is covered on a 150 mm circular heating plate 2, and the inner diameter of the gasket is 140 mm. The cover plate 1 is a quartz disc with a diameter of 150 mm, which is fixed by a snap to form a closed gap cavity. The solution circulation system is also connected to the liquid inlet and outlet. The storage container contains a saturated FAPbI3 / GBL solution, which is initially maintained at 120°C. First, a high-temperature saturated solution (about 100°C) is injected into the gap, and then the temperature of the right half of the heating plate is set to drop from 100°C to 70°C at a rate of -5°C per hour, while the left half is maintained at 100°C. In this way, supersaturation is formed during the gradual cooling process on the right side, inducing nucleation and growth on the right side first. When crystals appear on the right side, the left area is cooled at a uniform rate to expand the crystals to the left. Since multiple crystal nuclei are inevitably formed in this process, the resulting wafer is polycrystalline. Finally, within about 18 hours, the entire 140 mm diameter area is filled with a perovskite crystal film with a thickness of about 0.1 mm. After cooling, the wafer is removed, and a dark black translucent film can be seen. XRD analysis revealed a perovskite phase with distinct polycrystalline diffraction peaks. Microscopic observation revealed grain sizes on the order of millimeters, significantly larger than the micron-sized grains of conventional solution-grown polycrystalline films. This film can be used as a light-absorbing layer in photovoltaic devices. Preliminary performance tests show that its carrier lifetime and cell efficiency are superior to those of devices prepared from conventional polycrystalline thin films. This example demonstrates that the apparatus of the present invention is also suitable for producing large-area, high-quality perovskite polycrystalline thin films. By adjusting the crystallization method and parameters, grain size and film thickness can be controlled.

[0054] The device provided by the specific embodiment of the present invention has the following advantages:

[0055] (1) Significantly shorten the growth cycle and increase the crystal size: Through dynamic solution circulation and optimized temperature gradient, the present invention effectively improves the mass transfer efficiency and crystallization rate of crystal growth. Perovskite wafers with a diagonal size of centimeters can be prepared in about 1 to 2 days. The growth time is shortened by several times compared with the traditional spatial confinement static method. The wafer size is increased from the millimeter level to the centimeter level, breaking through the crystal size limitation of existing methods.

[0056] (3) High crystal quality and regular morphology: The strategy of confined space and slow controlled supersaturation helps to obtain regular and complete crystal morphology. Single crystal wafers have no grain boundaries and extremely low defect density; for polycrystalline sheets, the grain size is large and the interface is clean.

[0057] (4) Strong operability and versatility: The device structure is clear and simple, and each component is easy to process and assemble. The growth process is easy to monitor and adjust. Perovskite precursors of different compositions (such as different cations or halogens) can be grown by adjusting the temperature gradient and solution supply rate, and the device has versatility. In addition, the device can be operated in a closed condition or immersed in an external solution, and the operation is flexible. Through scale-up design, multiple crystals can be grown simultaneously, and it has the potential for large-scale production.

[0058] In summary, the device and its supporting method provided by the present application effectively solve the technical problem of rapidly preparing large-size high-quality perovskite single crystal / polycrystalline sheets, and have high efficiency and high quality. The perovskite single crystal wafers obtained by the present application can be directly applied to photovoltaic solar cells, X-ray imaging detectors, photoelectric sensors, light-emitting diodes and other fields, and are expected to significantly improve the performance and stability of these devices. The technical solution of the present application has reasonable structure and clear steps, and is easy to realize industrialization, which has important significance for the development of new photovoltaic materials such as perovskite.

[0059] The above only describes the preferred embodiments of the present application, and it should be understood that the present application is not limited to the above specific content. For those skilled in the art, various modifications and equivalent replacements can be made without departing from the principles of the present application, and these modifications and replacements should also be considered as falling within the protection scope of the present application. In particular, the size, material and specific structure of the device of the present application can be changed according to actual needs, and the temperature gradient setting and solution system selection can be optimized for different perovskite materials. The protection scope of the present application is defined by the scope of the claims.

Claims

1. A device for preparing large-sized perovskite single crystals or multi-crystals, characterized in that: include: A perovskite single crystal or polycrystalline growth system, wherein a heating plate is provided inside or at the bottom of the perovskite single crystal or polycrystalline growth system, and the heating plate is composed of a plurality of heating units arranged in an array; a precursor solution circulation system connected to the perovskite single crystal or polycrystalline growth system and configured to circulate a perovskite precursor solution with the perovskite single crystal or polycrystalline growth system; A temperature control system is connected to the heating unit and is used to control the temperature of the heating unit to form a target temperature difference between the heating units in order to induce nucleation during the nucleation induction stage. It is also used to maintain or expand the temperature difference in the crystal-free region during the crystal growth stage to maintain the crystal front in a supersaturated state to achieve crystal growth. It is also used to adjust the temperature of the heating unit after obtaining a perovskite single crystal or multi-crystal crystal of a target size so that the temperature of the heating plate drops to room temperature.

2. The device for preparing large-size perovskite single crystals or multi-crystals according to claim 1, characterized in that: During the nucleation induction stage, the temperature control system controls the temperature of the heating unit to reach the target temperature difference within 6-12 hours.

3. The device for preparing large-sized perovskite single crystals or multi-crystals according to claim 1, characterized in that: During the nucleation induction stage, the temperature control system controls the temperature of the heating unit so that the temperature of the middle area and the temperature of the two end areas of the heating plate form a target temperature difference.

4. The device for preparing large-size perovskite single crystals or multi-crystals according to claim 1, characterized in that: After obtaining the target size of perovskite single crystal or polycrystalline wafers, the temperature control system adjusts the temperature of the heating unit so that the heating plate drops to room temperature within 1-2 hours, and at the same time the precursor solution circulation system stops supplying perovskite precursor solution to the perovskite single crystal or polycrystalline growth system.

5. The device for preparing large-sized perovskite single crystal or multi-crystal according to claim 1, characterized in that: The surface of the heating plate is coated with polytetrafluoroethylene hydrophobic material.

6. The device for preparing large-sized perovskite single crystals or multi-crystals according to claim 1, characterized in that: The width of each heating unit is 1-10 mm and the length is 10-500 mm.

7. The device for preparing large-sized perovskite single crystals or multi-crystals according to claim 1, characterized in that: The precursor solution circulation system further includes a gasket and a cover plate; The gasket is located between the heating plate and the cover plate. The gasket is arranged at the edge of the heating plate. A gap is provided between the gaskets. The gap enables the precursor solution circulation system to provide and receive the perovskite precursor solution, thereby realizing the circulation of the perovskite precursor solution. The gasket is also used to adjust the distance between the heating plate and the cover plate. The cover plate is used to limit the growth direction of the perovskite single crystal or polycrystal, so that the perovskite single crystal or polycrystal grows laterally.

8. The device for preparing large-sized perovskite single crystals or multi-crystals according to claim 1, characterized in that: The gasket may also be a sealing ring gasket, which can form a closed space with the cover plate and the heating plate. The precursor solution circulation system provides and receives the perovskite precursor solution to the closed space through the sealing ring gasket, thereby realizing the circulation of the perovskite precursor solution.

9. The device for preparing large-sized perovskite single crystals or multi-crystals according to claim 1, characterized in that: The precursor solution circulation system comprises: A solution storage container, used for storing a saturated perovskite precursor solution; An infusion pump, an inlet pipe, and a liquid outlet pipe, one end of each of which is connected to the precursor solution circulation system and the other end is connected to the solution storage container. The perovskite precursor solution in the solution storage container is introduced into the perovskite single crystal or polycrystalline growth system through the infusion pump through the liquid inlet pipe, and the perovskite precursor solution in the perovskite single crystal or polycrystalline growth system is recovered to the solution storage container through the liquid outlet pipe to achieve a circulating flow. A flow control device is connected to the infusion pump and is used to adjust the circulation speed of the perovskite precursor solution, or automatically replenish the perovskite precursor solution to the perovskite single crystal or polycrystalline growth system after detecting that the concentration of the perovskite precursor solution in the perovskite single crystal or polycrystalline growth system drops to a set value.

10. The device for preparing large-sized perovskite single crystals or multi-crystals according to claim 1, characterized in that: The perovskite precursor solution refers to MAPbI3, MAPbBr3, MAPbCl3, FAPbI3, FAPbBr3, FAPbCl3, CsPbI3, CsPbBr3, CsPbCl3, and blended precursor solutions thereof.

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