Method for growing organic-inorganic hybrid perovskite single crystal

Abstract

The invention discloses a method for growing an organic-inorganic hybrid perovskite single crystal, belongs to the field of organic-inorganic hybrid perovskite materials, and provides a method for solving the problem that the defect density of a single crystal obtained by a current inverse temperature method-space confinement method is relatively large from the perspective of growth speed control. On the basis of a sealed growth system, the solubility inverse temperature characteristic of the single crystal in a specific solvent is utilized, the growth speed of the crystal is regulated and controlled through temperature, the size and surface appearance of the single crystal can be regulated and controlled, and meanwhile, the crystal has lower defect density, lower internal stress, less lattice distortion and higher crystal quality. The method can be applied to subsequent semiconductor device manufacturing without further deep processing or only simple processing, such as a solar cell and a ray detector.

Description

Technical Field

[0001] The invention belongs to the field of organic-inorganic hybrid perovskite materials, and in particular relates to a method for growing an organic-inorganic hybrid perovskite single crystal. Background Art

[0002] Organic-inorganic hybrid perovskite has long carrier lifetime, high carrier mobility, and long carrier diffusion length, which make it excellent in various optoelectronic devices such as solar cells, photodetectors, lasers, optical fibers, field effect transistors, etc. Compared with traditional silicon-based semiconductor materials, the production cost of organic-inorganic hybrid perovskite materials is lower and the process is simpler.

[0003] Compared with polycrystalline perovskite materials, single-crystal perovskite materials have more outstanding advantages because they eliminate grain boundaries, and the device performance is better. They are also better than polycrystalline materials in terms of device stability, an important indicator. At present, the development of perovskite batteries is very rapid, and the efficiency has increased from 3.8% in 2009 to 26.1% in 2024.

[0004] At present, the methods for preparing perovskite single crystals mainly include cooling method, reverse temperature method, anti-solvent diffusion method, Bridgman method, etc. Among them, the reverse temperature method is widely used because it can obtain high-quality crystals quickly and is easier to control. This method can be combined with the spatial confinement method to obtain single crystals of the desired shape and size.

[0005] The literature Single-crystal perovskite solar cells exhibit close to half amillimeter electron diffusion length (Advance Materials, Volume 34, Issue 47, November 24, 2022) uses the inverse temperature method combined with the spatial confinement method to obtain single crystals of target thickness. Although this method is relatively convenient and fast, the single crystals obtained by increasing the temperature at a certain rate are often accompanied by a large defect density. Therefore, a preparation method that can obtain crystals of specified size and morphology while taking into account low defect density and easy operation is needed. Summary of the invention

[0006] In view of the problem that the single crystal defect density obtained by the current inverse temperature method-spatial confinement method is large, the present invention will propose a method to solve the problem from the perspective of growth rate control. This method for preparing single crystals requires low cost, simple equipment, simple process, high raw material utilization rate, and can be promoted on a large scale. The technical solution adopted by the present invention is as follows: A method for growing an organic-inorganic hybrid perovskite single crystal, the specific steps are as follows: 1) AX and PbX2 are measured in a molar ratio of 1: (1.0-1.5), heated and stirred in an organic solvent to fully dissolve them, and a 1.5 mol / L precursor solution is prepared; the AX is a combination of one or more of iodomethylamine, bromomethylamine, and chloromethylamine, and the PbX2 is a combination of one or more of lead iodide, lead bromide, and lead chloride; the organic solvent is selected according to the solubility inverse temperature characteristic; 2) Filter the precursor solution to remove insoluble matter and dust introduced during the preparation process; 3) Using a syringe to inject the precursor solution into a sealed crystal growth device; the crystal growth device is composed of two layers of glass sheets and a sealing ring in the middle, the thickness of the sealing ring is selected according to the thickness of the single crystal, and there is a cavity between the upper and lower glass sheets for injecting the precursor solution to grow the crystal; 4) Keep the crystal growth device injected with the precursor solution warm. The warming temperature should be lower than the temperature at which the crystal begins to nucleate. The warming time should be more than 12 hours to make the temperature in the chamber consistent, so as to avoid the destruction of the surface morphology and the generation of a large number of additional defects caused by repeated dissolution of the crystal. 5) Slowly increase the temperature until crystals precipitate under microscope observation, and then use gradient heating to make the crystals grow at a uniform rate, and the growth rate should be ≤1 mm 3 / h, take out the crystal when the substrate temperature reaches 60~100 ℃; 6) Removing the surface solution to obtain an organic-inorganic hybrid perovskite single crystal.

[0007] Preferably, in step 1), the molar ratio of AX to PbX2 is 1:(1.05-1.10).

[0008] Preferably, the organic solvent in step 1) is one of GBL (γ-butyrolactone), DMF (N,N-dimethylformamide), and DMSO (dimethyl sulfoxide); Preferably, in step 2), a 0.22 μm filter head is used for filtering the precursor solution.

[0009] Preferably, in step 3), the edges of the upper and lower glass sheets of the crystal growing device are sealed with silicone rubber; Preferably, the upper and lower glass sheets of the crystal growing device in step 3) are float glass with hydrophobic surface treatment; Preferably, the sealing ring of the crystal growing device in step 3) is made of polytetrafluoroethylene to avoid interaction between the solvent and other materials.

[0010] Preferably, in step 5), the horizontal cross-section size of the single crystal observed before the gradient heating is ≤1 mm×1 mm; Preferably, the growth rate of the crystal in step 5) should be greater than 0.15 mm3 / h to reduce the impact of additional nucleation centers on the edge on the speed.

[0011] Preferably, the surface of the organic-inorganic hybrid perovskite single crystal obtained in step 6) is cleaned with an anti-solvent after polishing.

[0012] Beneficial effects of the present invention: 1. The present invention uses a pair of glass substrates and seals them to construct the cavity required for crystal growth. After the growth system is sealed, the effect of solvent volatilization on the crystal precipitation rate and position in the system is greatly reduced, which is also the prerequisite for subsequent regulation of the growth rate.

[0013] 2. The present invention uses the inverse temperature characteristic of the solubility of single crystals in specific solvents based on a sealed growth system to regulate the growth rate of the crystals by temperature, thereby achieving regulation of the size and surface morphology of the single crystals, and having lower defect density, lower internal stress, less lattice distortion, and higher crystal quality. It can be applied to subsequent semiconductor device manufacturing, such as solar cells and radiation detectors, without further processing or with only simple processing.

[0014] 3. By changing the raw materials, growth rate, reaction temperature, precursor concentration and substrate thickness, other organic-inorganic hybrid perovskite single crystals can be grown at a controlled rate. The required reaction conditions and related operations are relatively simple, do not require complex equipment, and have high repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the rocking curve of the methylamine lead bromide single crystal grown by the reverse temperature method in Comparative Example 1.

[0016] Figure 2 This is the rocking curve of the methylamine lead bromide single crystal grown by the reverse temperature method in Comparative Example 2.

[0017] Figure 3 This is the rocking curve of the methylamine lead iodine single crystal grown by the rate control method in Example 1.

[0018] Figure 4 This is the rocking curve of the methylamine lead iodine single crystal grown by the rate control method in Example 2.

[0019] Figure 5 The temperature-time curve of the gradient heating used to control the crystal growth rate in Example 1 is Figure 6 This is a structural diagram of the growth chamber used in the speed control method in Example 1 and Example 2; in the figure, 1 is a float glass sheet, and 2 is a polytetrafluoroethylene sealing ring. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is explained and illustrated in the form of specific embodiments below.

[0021] Comparative Example 1 (Growing methylamine lead bromide single crystal by reverse temperature method) (a) Preparation of methylamine bromide: A certain amount of methylamine aqueous solution (40%wt) is added to a three-necked bottle with a stirrer in advance. In an ice-water bath, a slightly excessive amount of hydrobromic acid (40%wt) is slowly added dropwise through a separatory funnel. At the same time, it is placed on a magnetic stirrer and stirred at a speed of 500r / m for more than four hours. During the stirring period, the system is always kept at a low temperature to fully mix the two to obtain a crude precursor solution. The solution is subjected to rotary evaporation, and the rotary evaporation equipment is cleaned before the rotary evaporation begins. After the solvent is completely removed by rotary evaporation, a crude product is obtained. At this time, the crude product may be white or light yellow. After dissolving and filtering the product, recrystallization begins. After heating to dissolve and filter out the insoluble matter, ether is added to the solution for recrystallization. If there are large insoluble blocks during the recrystallization process, use a glass rod to break them up and continue heating. After washing the powder obtained therein with ice ethanol, the obtained solution is filtered using a Buchner funnel, and the powder product obtained by filtration is recrystallized repeatedly according to the above operation for at least three times to obtain the final product, which is placed in a vacuum drying oven and vacuum dried at a constant temperature of 50°C to remove the residual solvent. After drying for 24 hours, the final product, methylamine bromide, is obtained in the form of a white powder, which is sealed and stored in an inert gas environment away from light.

[0022] (b) Preparation of precursor solution methylamine lead bromide: Methylamine bromide and lead bromide powders in a molar ratio of 1:1 were measured, and N,N-dimethylformamide was used to prepare a 1.5 mol / L solution, and the solution was stirred at room temperature for 5 h using a magnetic stirrer to obtain a precursor solution.

[0023] (c) Growth chamber structure: Take a number of round (Φ100mm) float glasses of equal size and thickness of 4 mm, drop 1ml of the prepared precursor solution on the glass plate, and then press another glass plate on it. Place the cavity on a heating table with a starting temperature of 30℃ and keep it warm for 12h. After the insulation is completed, start to increase the temperature uniformly at a rate of 1℃ / h to 60℃. A large number of methylamine lead bromide single crystals of the required thickness are obtained. Its rocking curve is shown in the attached figure. Figure 1 shown.

[0024] This comparative example utilizes the characteristic that the solubility of methylamine lead bromide in a specific solvent N,N-dimethylformamide decreases as the temperature rises, and grows methylamine lead bromide single crystals by the inverse temperature method. However, without controlling the growth rate, the half-peak width of the rocking curve of the obtained single crystal is relatively wide, which is caused by insufficient local solution, part of the crystal cannot contact the saturated solution, and the growth is hindered. This area with high and low differences hinders the application of the obtained single crystal, and complex surface treatment is required before it can be used as an active layer. At the same time, the defect density of the single crystal is high, which affects the performance of the device.

[0025] Comparative Example 2 (Growing methylamine lead iodine single crystal by reverse temperature method) (a) Preparation of methylamine iodide: A certain amount of methylamine aqueous solution (40%wt) is added to a three-necked bottle with a stirrer in advance. Under ice-water bath conditions, a slightly excessive amount of hydroiodic acid (55%wt) is slowly added dropwise through a separatory funnel. At the same time, it is placed on a magnetic stirrer and stirred at a speed of 500r / m for more than four hours. During the stirring period, the system is always kept at a low temperature so that the two are fully mixed to obtain a crude precursor solution. The solution is subjected to rotary evaporation, and the rotary evaporation equipment is cleaned before the rotary evaporation begins. After the solvent is completely removed by rotary evaporation, a crude product is obtained. At this time, the crude product may be white or light yellow. After dissolving and filtering the product, recrystallization begins. After heating to dissolve and filter out the insoluble matter, ether is added to the solution for recrystallization. If there are large insoluble blocks during the recrystallization process, use a glass rod to break them up and continue heating. After washing the powder obtained therein with ice ethanol, the obtained solution is filtered using a Buchner funnel, and the powder product obtained by filtration is recrystallized repeatedly according to the above operation for at least three times to obtain the final product, which is placed in a vacuum drying oven and vacuum dried at a constant temperature of 50°C to remove the residual solvent. After drying for 24 hours, the final product, methylamine iodide, is obtained in the form of a white powder, which is sealed and stored in an inert gas environment away from light.

[0026] (b) Preparation of precursor solution methylamine lead iodine: Methylamine iodide and lead iodide powders in a molar ratio of 1:1 were measured, and γ-butyrolactone was used to prepare a 1.5 mol / L solution, which was stirred at 70° C. for 5 h using a magnetic stirrer to obtain a precursor solution.

[0027] (c) Growth chamber structure: Take several round (Φ100mm) float glasses of equal size and thickness of 4 mm, put gaskets of the required single crystal thickness between pairs of glasses, and use silicone rubber to seal and bond them together. Try to avoid rubber entering the inside of the glass during the process. After bonding, wait for the rubber to fully solidify and then use it as a sealed cavity for growth. Inject the above precursor solution into the cavity using a syringe. During the injection process, observe the sealing of the cavity and repair any leaks in time. After the cavity is filled, seal the injection position and place the cavity on a heating table with a starting temperature of 70°C. Keep it warm for 12 hours. After the insulation is completed, start to heat it uniformly at a rate of 1°C / h to 120°C to obtain a large number of methylamine lead iodine single crystals of the required thickness. Its rocking curve is shown in the attached figure. Figure 2 shown.

[0028] This comparative example utilizes the characteristic that the solubility of methylamine lead iodine in a specific solvent γ-butyrolactone decreases with increasing temperature, and grows methylamine lead iodine single crystals by the inverse temperature method. However, under the condition of not controlling the growth rate, the surface of the obtained single crystal has a larger height difference than the control group, which is caused by insufficient local solution, a part of the crystal cannot contact the saturated solution, and the growth is hindered. This area with height difference has hindered the application of the obtained single crystal, and complex surface treatment is required to be used as an active layer. At the same time, the defect density of the single crystal is high, which affects the performance of the device.

[0029] Example 1 (Growing high-quality methylamine lead bromide single crystals by speed control method) (a) Preparation of methylamine bromide: A certain amount of methylamine aqueous solution (40%wt) is added to a three-necked bottle with a stirrer in advance. In an ice-water bath, a slightly excessive amount of hydrobromic acid (40%wt) is slowly added dropwise through a separatory funnel. At the same time, it is placed on a magnetic stirrer and stirred at a speed of 500r / m for more than four hours. During the stirring period, the system is always kept at a low temperature to fully mix the two to obtain a crude precursor solution. The solution is subjected to rotary evaporation, and the rotary evaporation equipment is cleaned before the rotary evaporation begins. After the solvent is completely removed by rotary evaporation, a crude product is obtained. At this time, the crude product may be white or light yellow. After dissolving and filtering the product, recrystallization begins. After heating to dissolve and filter out the insoluble matter, ether is added to the solution for recrystallization. If there are large insoluble blocks during the recrystallization process, use a glass rod to break them up and continue heating. After washing the powder obtained therein with ice ethanol, the obtained solution is filtered using a Buchner funnel, and the powder product obtained by filtration is recrystallized repeatedly according to the above operation for at least three times to obtain the final product, which is placed in a vacuum drying oven and vacuum dried at a constant temperature of 50°C to remove the residual solvent. After drying for 24 hours, the final product, methylamine bromide, is obtained in the form of a white powder, which is sealed and stored in an inert gas environment away from light.

[0030] (b) Preparation of precursor solution methylamine lead bromide: Methylamine bromide and lead bromide powders in a molar ratio of 1:1 were measured, and N,N-dimethylformamide was used to prepare a 1.5 mol / L solution, and the solution was stirred with a magnetic stirrer for 5 h to obtain a precursor solution.

[0031] (c) Growth chamber structure: Take a number of round (Φ100mm) float glasses of equal size and thickness of 4 mm, put a gasket of the required single crystal thickness between the pairs of glasses, and use silicone rubber to seal and bond them together. Try to avoid rubber entering the inside of the glass during the process. After bonding, wait for the rubber to fully solidify, and then it can be used as a sealing cavity for growth (such as Figure 6 As shown). The above precursor solution was injected into the cavity using a syringe. During the injection process, the sealing of the cavity was observed and leaks were repaired in time. After the cavity was filled, the injection position was sealed and the cavity was placed on a heating table with a starting temperature of 30°C for 12 hours. After the insulation was completed, the temperature was raised uniformly at a rate of 0.5°C / h to 42°C. After the temperature was stabilized for 2 hours, the temperature was gradually raised. The relationship between temperature and time is shown in Figure 5 As shown in (the specific amount can be determined based on the relationship between the solubility of the perovskite material in the organic solvent and the temperature), the crystal growth rate is adjusted to 1 mm by this heating method. 3 / h, and cut off at 60℃, to obtain a large number of methylamine lead bromide single crystals with smooth surface.

[0032] By comparing the crystals obtained by the growth method described in this embodiment with the crystals obtained by the normal inverse temperature method, it can be found that the crystals obtained in this embodiment are more regular and more transparent. Figure 3 shown.

[0033] X-ray diffraction rocking curves of the crystals prepared by the methods of Example 1 and Comparative Example 1 ( Figure 1 , Figure 3 ) can be found that the single crystal grown by the method of Example 1 has higher crystallinity.

[0034] This embodiment obtains high-quality, low-defect-density single crystals by controlling the growth rate. By observing the crystals with continuous temperature increase, the temperature increase rate is adjusted under the growth rate condition, so that the single crystal can grow at a certain speed in a controllable manner, reducing the high defect density caused by disordered growth.

[0035] The method of this embodiment utilizes the characteristic that the solubility of methylamine lead bromide in a specific solvent N,N-dimethylformamide decreases with increasing temperature, and regulates the growth rate near the observed nucleation start temperature position to achieve the effect of controllable crystal growth rate. Compared with the traditional anti-solvent method, the method of this embodiment can achieve the regulation of single crystal size and surface morphology, and at the same time has lower defect density, lower internal stress and less lattice distortion, and higher crystal quality. It can be applied to subsequent semiconductor device manufacturing, such as solar cells and radiation detectors, without further deep processing or only simple processing.

[0036] Example 2 (Growing high-quality methylamine lead iodine single crystals by speed control method) (a) Preparation of methylamine iodide: A certain amount of methylamine aqueous solution (40%wt) is added to a three-necked bottle with a stirrer in advance. Under ice-water bath conditions, a slightly excessive amount of hydroiodic acid (55%wt) is slowly added dropwise through a separatory funnel. At the same time, it is placed on a magnetic stirrer and stirred at a speed of 500r / m for more than four hours. During the stirring period, the system is always kept at a low temperature so that the two are fully mixed to obtain a crude precursor solution. The solution is subjected to rotary evaporation, and the rotary evaporation equipment is cleaned before the rotary evaporation begins. After the solvent is completely removed by rotary evaporation, a crude product is obtained. At this time, the crude product may be white or light yellow. After dissolving and filtering the product, recrystallization begins. After heating to dissolve and filter out the insoluble matter, ether is added to the solution for recrystallization. If there are large insoluble blocks during the recrystallization process, use a glass rod to break them up and continue heating. After washing the powder obtained therein with ice ethanol, the obtained solution is filtered using a Buchner funnel, and the powder product obtained by filtration is recrystallized repeatedly according to the above operation for at least three times to obtain the final product, which is placed in a vacuum drying oven and vacuum dried at a constant temperature of 50°C to remove the residual solvent. After drying for 24 hours, the final product, methylamine iodide, is obtained in the form of a white powder, which is sealed and stored in an inert gas environment away from light.

[0037] (b) Preparation of precursor solution methylamine lead iodine: Methylamine iodide and lead iodide powders in a molar ratio of 1:1 were measured, and γ-butyrolactone was used to prepare a 1.5 mol / L solution, which was stirred at 70° C. for 5 h using a magnetic stirrer to obtain a precursor solution.

[0038] (c) Growth chamber structure: Take a number of round (Φ100mm) float glasses of equal size and thickness of 4 mm, put a gasket of the required single crystal thickness between the pairs of glasses, and use silicone rubber to seal and bond them together. Try to avoid rubber entering the inside of the glass during the process. After bonding, wait for the rubber to fully solidify, and then it can be used as a sealing cavity for growth (such as Figure 6As shown). The above precursor solution was injected into the cavity using a syringe. During the injection process, the sealing of the cavity was observed and leaks were repaired in time. After the cavity was filled, the injection position was sealed. The cavity was placed on a heating table with a starting temperature of 70°C and kept warm for 12 hours. After the insulation was completed, the temperature was uniformly increased to 90°C at a rate of 1°C / h. After the temperature was stabilized for 2 hours, the temperature was gradually increased. The process and growth rate were similar to those in Example 1. The crystal growth rate was adjusted to 1 mm by adjusting the heating method. 3 / h. When the temperature reaches 120℃, a large amount of methylamine lead iodine single crystals with smooth surface are obtained.

[0039] The rocking curve test of the crystals prepared by the two methods of this embodiment and comparative example 2 ( Figure 2 , Figure 4 ) can be found that the single crystal grown by the method of this embodiment has better crystallinity.

[0040] This embodiment obtains high-quality, low-defect density single crystals by controlling the growth rate. By observing the crystals with continuous heating, the heating rate is adjusted under the growth rate condition so that the single crystals can grow at a certain controllable rate, thereby reducing the high defect density caused by disordered growth.

[0041] This embodiment utilizes the characteristic that the solubility of methylamine lead iodine in a specific solvent γ-butyrolactone decreases with increasing temperature, and regulates the growth rate near the observed nucleation start temperature position to achieve the effect of controllable crystal growth rate. Compared with the traditional anti-solvent method, the method of this embodiment can achieve the regulation of single crystal size and surface morphology, and at the same time has lower defect density, lower internal stress and less lattice distortion, and higher crystal quality. It can be applied to subsequent semiconductor device manufacturing, such as solar cells and radiation detectors, without further deep processing or only simple processing.

Claims

1. A method for growing an organic-inorganic hybrid perovskite single crystal, characterized in that: The specific steps of this method are as follows: 1) AX and PbX2 are measured in a molar ratio of 1: (1.0-1.5), heated and stirred in an organic solvent to fully dissolve them, and a 1.5 mol / L precursor solution is prepared; the AX is a combination of one or more of iodomethylamine, bromomethylamine, and chloromethylamine, and the PbX2 is a combination of one or more of lead iodide, lead bromide, and lead chloride; the organic solvent is selected according to the solubility inverse temperature characteristic; 2) Filter the precursor solution to remove insoluble matter and dust introduced during the preparation process; 3) Using a syringe to inject the precursor solution into a sealed crystal growth device; the crystal growth device is composed of two layers of glass sheets and a sealing ring in the middle, the thickness of the sealing ring is selected according to the thickness of the single crystal, and there is a cavity between the upper and lower glass sheets for injecting the precursor solution to grow the crystal; 4) Keep the crystal growth device injected with the precursor solution warm. The warming temperature should be lower than the temperature at which the crystal begins to nucleate, and the warming time should be more than 12 hours. 5) Slowly increase the temperature until crystals precipitate under microscope observation, and then use gradient heating to make the crystals grow at a uniform rate, and the growth rate is ≤1mm 3 / h, take out the crystal when the substrate temperature reaches 60~100℃; 6) Removing the surface solution to obtain an organic-inorganic hybrid perovskite single crystal.

2. The method for growing an organic-inorganic hybrid perovskite single crystal according to claim 1, characterized in that: In step 1), the molar ratio of AX to PbX2 is 1:(1.05~1.10).

3. The method for growing an organic-inorganic hybrid perovskite single crystal according to claim 1, characterized in that: In step 1), the organic solvent is one of γ-butyrolactone, N,N-dimethylformamide and dimethyl sulfoxide.

4. The method for growing an organic-inorganic hybrid perovskite single crystal according to claim 1, characterized in that: In step 2), the precursor solution is filtered using a 0.22 μm filter head.

5. The method for growing an organic-inorganic hybrid perovskite single crystal according to claim 1, characterized in that: In step 3), the edges of the upper and lower glass sheets of the crystal growing device are sealed using silicone rubber.

6. The method for growing an organic-inorganic hybrid perovskite single crystal according to claim 1, characterized in that: In step 3), the upper and lower glass sheets of the crystal growing device are made of float glass with hydrophobic surface treatment.

7. The method for growing an organic-inorganic hybrid perovskite single crystal according to claim 1, characterized in that: In step 3), the sealing ring of the crystal growing device is made of polytetrafluoroethylene.

8. The method for growing an organic-inorganic hybrid perovskite single crystal according to claim 1, characterized in that: Step 5) The horizontal cross-section size of the single crystal observed before the gradient heating is ≤1 mm×1 mm.

9. The method for growing an organic-inorganic hybrid perovskite single crystal according to claim 1, characterized in that: In step 5), the growth rate of the crystal should be greater than 0.15 mm 3 / h.

10. The method for growing an organic-inorganic hybrid perovskite single crystal according to claim 1, characterized in that: Step 6) The obtained organic-inorganic hybrid perovskite single crystal is further cleaned using an anti-solvent after polishing.

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