Perovskite particle preparation method, solar cell, and tandem solar cell

Abstract

This application relates to a method for preparing perovskite particles, a solar cell, and a tandem solar cell. The method for preparing perovskite particles includes: dissolving organic and inorganic raw materials in a growth mother liquor and mixing them thoroughly to obtain a mixed solution; adjusting the reaction conditions of the mixed solution to bring it into the critical nucleation state of the perovskite particles; subjecting the mixed solution in the critical nucleation state to ultrasonic pulse stimulation, and after a preset time, screening out the perovskite particles from the mixed solution. The embodiments of this application facilitate the simple and efficient synthesis of large quantities of perovskite particles, improve the synthesis efficiency of raw materials for perovskite solar cells, and facilitate the mass production of perovskite solar cell wafers.

Description

Cross-references to related applications

[0001] This application is a divisional application of Chinese invention patent application filed on December 13, 2022, with application number 202211601000.8 and invention title "Method for preparing perovskite particles, solar cell and tandem solar cell". Background Technology

[0002] Fossil fuels cause air pollution and have limited reserves, while solar energy has advantages such as being clean, pollution-free, and abundant. Therefore, solar energy is gradually becoming the core clean energy source to replace fossil fuels. Due to the excellent photoelectric conversion efficiency of solar cells, solar cells have become the focus of development for clean energy utilization.

[0003] One crucial factor influencing the proportion of solar energy in energy utilization is the photoelectric conversion efficiency of solar cells. Optimizing and improving the structural design and material composition of solar cells is a fundamental approach to enhancing this efficiency. Perovskite solar cells, due to their long lifespan and relatively stable photoelectric conversion efficiency, have promising development prospects.

[0004] However, current perovskite solar cells suffer from low manufacturing efficiency and difficulty in mass production. Summary of the Invention

[0005] This application provides a method for preparing perovskite particles, a solar cell, and a tandem solar cell, which at least facilitates the simple and efficient synthesis of large quantities of perovskite particles, improves the synthesis efficiency of raw materials for perovskite solar cells, and makes it easier to mass-produce perovskite solar cell wafers.

[0006] This application provides a method for preparing perovskite particles, comprising: dissolving organic raw materials and inorganic raw materials in a growth mother liquor and mixing them thoroughly to obtain a mixed solution; adjusting the reaction conditions of the mixed solution to bring the mixed solution into the nucleation critical state of perovskite particles; subjecting the mixed solution that has entered the nucleation critical state to ultrasonic pulse stimulation, and after a preset time, screening out the perovskite particles from the mixed solution.

[0007] In addition, the ultrasonic pulse stimulation of the mixed solution that has entered the nucleation critical state includes: using ultrasonic waves with a frequency of 1 Hz to 1 MHz to stimulate the mixed solution that has entered the nucleation critical state with ultrasonic pulses.

[0008] In addition, the duration of the ultrasonic pulse stimulation is from 0.001 s to 1 s.

[0009] In addition, the step of screening the perovskite particles in the mixed solution after a preset time includes: screening the target perovskite particles in the mixed solution, wherein the maximum distance between any two points on the outer surface of the target perovskite particles is 5 micrometers to 100 micrometers.

[0010] In addition, after screening out the target perovskite particles, the method further includes: redissolving the remaining particles other than the target perovskite particles in the growth mother liquor or the mixed solution.

[0011] In addition, the preset duration includes 1 minute to 2 hours.

[0012] In addition, after subjecting the mixed solution that has entered the nucleation critical state to ultrasonic pulse stimulation, the method further includes: adjusting the temperature of the mixed solution to 50℃-150℃.

[0013] In addition, adjusting the reaction conditions of the mixed solution includes adjusting the temperature of the mixed solution to 25℃-150℃.

[0014] In addition, before dissolving the organic and inorganic raw materials in the growth mother liquor, the method further includes: determining the molar mass ratio of each element in the perovskite particles according to the target band gap of the perovskite particles; and weighing the organic and inorganic raw materials according to the molar mass ratio of each element in the perovskite particles.

[0015] In addition, the target band gap includes 1 eV to 2 eV.

[0016] Accordingly, this application also provides a solar cell, comprising: a first conductive layer, a first carrier transport layer, a perovskite absorber layer, and a second conductive layer stacked sequentially, wherein the perovskite absorber layer comprises a plurality of perovskite particles, and the perovskite particles are formed by the perovskite particle preparation method described above.

[0017] In addition, the first carrier transport layer is a hole transport layer or an electron transport layer.

[0018] In addition, the solar cell further includes a second carrier transport layer, which is located between the perovskite absorber layer and the second conductive layer, and is in contact with the perovskite absorber layer and the second conductive layer, respectively.

[0019] Furthermore, when the first carrier transport layer is a hole transport layer, the second carrier transport layer is an electron transport layer; when the first carrier transport layer is an electron transport layer, the second carrier transport layer is a hole transport layer.

[0020] A corresponding embodiment of this application also provides a tandem solar cell, comprising: a top cell, an adhesive layer, and a bottom cell stacked sequentially, wherein the top cell is a solar cell as described above.

[0021] In addition, the bottom cell includes crystalline silicon solar cells, CIGS thin-film solar cells, cadmium telluride thin-film solar cells, III-V thin-film solar cells, or narrow bandgap perovskite thin-film solar cells.

[0022] In addition, the bonding layer includes a mechanical bonding layer made of conductive adhesive.

[0023] The technical solution provided in this application has at least the following advantages: In the perovskite particle preparation scheme provided in this application embodiment, after dissolving organic and inorganic raw materials in the growth mother liquor and mixing them thoroughly to obtain a mixed solution, the reaction conditions of the mixed solution are adjusted according to the characteristics of perovskite particles to bring the reaction system in the mixed solution to the critical nucleation state of the perovskite particles. By adjusting the reaction system in the mixed solution to the critical nucleation state of the perovskite particles, the difficulty and time required for perovskite particle nucleation are reduced, and the nucleation efficiency and probability of perovskite particles are improved. Then, the mixed solution in which the reaction system has entered the critical nucleation state is subjected to ultrasonic pulse stimulation, and perovskite particles are screened out from the mixed solution after a preset time. By applying ultrasonic pulse stimulation to the mixed solution in which the reaction system is in the critical nucleation state, the extreme reaction conditions such as instantaneously generated high temperature, high pressure and extremely high cooling rate are utilized to greatly increase the number of perovskite particles nucleated in the mixed solution, making it easier to screen out a large number of perovskite particles from the mixed solution after a preset time, greatly improving the synthesis efficiency of perovskite particles, improving the raw material production efficiency of perovskite solar cells, and facilitating the mass production of perovskite solar cells. Attached Figure Description

[0024] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments, and unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0025] Figure 1 A flowchart illustrating a method for preparing perovskite particles according to an embodiment of this application; Figure 2 This is a schematic diagram of the structure of a solar cell provided in another embodiment of this application; Figure 3 This is a schematic diagram of another solar cell structure provided in an embodiment of this application; Figure 4 This is a schematic diagram of a stacked solar cell provided in another embodiment of this application. Detailed Implementation

[0026] As can be seen from the background technology, perovskite solar cells have good development prospects due to their advantages in lifespan and photoelectric conversion efficiency. However, the current perovskite solar cell manufacturing efficiency is low and mass production is difficult.

[0027] One embodiment of this application provides a method for preparing perovskite particles. In the process of preparing perovskite particles, after dissolving the raw materials in a growth mother liquor and mixing them thoroughly to obtain a mixed solution, the reaction conditions of the mixed solution are adjusted to bring the reaction system in the mixed solution to the critical nucleation state of the perovskite particles. By adjusting the reaction system in the mixed solution to the critical nucleation state of the perovskite particles, the difficulty and time required for perovskite particle nucleation are reduced, and the nucleation efficiency and probability of perovskite particles are improved. Then, the mixed solution in the critical nucleation state is subjected to ultrasonic pulse stimulation, and perovskite particles are screened out from the mixed solution after a preset time. By applying ultrasonic pulse stimulation to the mixed solution in the critical nucleation state, the extreme reaction conditions such as instantaneously generated high temperature, high pressure, and extremely high cooling rate greatly increase the number of perovskite particles nucleated in the mixed solution, making it easier to obtain a large number of perovskite particles after a preset time. This greatly improves the synthesis efficiency of perovskite particles, avoids the constraint of raw material synthesis efficiency on the production of perovskite solar cells, and facilitates the mass production of perovskite solar cells.

[0028] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0029] One embodiment of this application provides a method for preparing perovskite particles, applicable to perovskite particle synthesis equipment, such as ultrasonic chemical equipment. The preparation process of perovskite particles can be referred to... Figure 1 This includes, but is not limited to, the following steps: Step 101: Dissolve the organic and inorganic raw materials in the growth mother liquor and mix them thoroughly to obtain a mixed solution.

[0030] In the process of preparing perovskite particles, the particle synthesis equipment first dissolves the weighed organic and inorganic raw materials in a pre-prepared growth mother liquor. Then, the growth mother liquor containing the organic and inorganic raw materials is thoroughly stirred, shaken, and ultrasonically treated to obtain a fully mixed and homogeneous solution. The growth mother liquor can be propylene carbonate, butyrolactone, or other solvents that have a certain coordination ability with perovskite.

[0031] It is worth mentioning that the specific types of raw materials and growth mother liquor can be determined based on the basic preparation method used for perovskite particle preparation. These basic methods include cooling crystallization, reverse-temperature crystallization, and antisolvent-assisted crystallization. The selection of raw materials and growth mother liquor can be referenced during the dissolution of raw materials and preparation of the growth mother liquor. For example, when using antisolvent-assisted crystallization as the basic preparation method, methylammonium bromide (MABr, CH3NH3Br) can be used as the organic raw material, lead bromide (PbBr2) as the inorganic raw material, and N,N-dimethylformamide (DMF, C3H7NO) as the growth mother liquor, with dichloromethane (CH2Cl2) as the antisolvent for the preparation of perovskite particles. When using the heated crystallization method as the basic preparation method, methylammonium iodide (MAI, CH3NH3I) and formamidinium iodide (FAI, (HC(NH2)2I)) can be used as organic raw materials, lead iodide (PbI2) as inorganic raw material, and propylene carbonate as the growth mother liquor to prepare perovskite particles. When using the cooled crystallization method as the basic preparation method, methylammonium iodide (MAI) can be used as organic raw material, and lead acetate trihydrate (Pb(CH2COOH)2) can be used as inorganic raw material. The preparation of perovskite particles involves using 3H2O as an inorganic raw material and hydroiodic acid (HI) as a growth mother liquor. The specific basic preparation method, raw materials, and growth mother liquor selected during particle preparation are not limited in the embodiments of this application.

[0032] In some embodiments, before dissolving the organic and inorganic raw materials in the growth mother liquor, the method further includes: determining the molar mass ratio of each element in the perovskite particles according to the target band gap of the perovskite particles; and weighing the organic and inorganic raw materials according to the molar mass ratio of each element in the perovskite particles.

[0033] Before synthesizing perovskite particles, the chemical formula of the perovskite particles to be synthesized can be determined based on the required band gap, i.e., the target band gap. Then, based on the chemical formula, the molar ratio of each element in the perovskite particles can be determined. After determining the molar ratio of each element in the perovskite particles to be synthesized, the different components in the organic material are adjusted according to the determined molar ratio, and then equimolar amounts of organic and inorganic raw materials are weighed.

[0034] For example, using propylene carbonate as the growth mother liquor, methylamine iodide (MAI, CH3NH3I) and formamidinium iodide (FAI, (HC(NH2)2I)) as organic raw materials, and lead iodide (PbI2) as the inorganic raw material, the chemical formula of the prepared perovskite particles is MA X FA 1－ XTake PbI3 as an example.

[0035] Before synthesizing perovskite particles, if the chemical formula of the perovskite particles is determined to be MA based on the target band gap, then... 0.25 FA 0.75 In the case of PbI3, the molar ratio of MAI to FAI in the organic raw material to be dissolved is adjusted to 1:3; if the chemical formula of the perovskite particles is determined to be MA based on the target band gap of the perovskite particles. 0.75 FA 0.25 In the case of PbI3, the molar ratio of MAI to FAI in the organic raw materials to be dissolved is adjusted to 3:1; if the chemical formula of the perovskite particles is determined to be MA based on the target band gap of the perovskite particles... 0.5 FA 0.5 In the case of PbI3, the molar ratio of MAI to FAI in the organic raw material to be dissolved should be adjusted to 1:1. Furthermore, during the adjustment of the components in the organic raw material, appropriate fine-tuning of the inorganic raw material is necessary to maintain a constant molar ratio of 1:1 between the organic and inorganic raw materials. After determining the molar ratio of each component in the organic raw material, the organic and inorganic raw materials should be weighed according to the determined molar ratio.

[0036] By determining the molar mass ratio of each element in the perovskite particles according to the target band gap of the perovskite particles to be synthesized, and weighing the raw materials according to the determined molar mass ratio, the prepared perovskite particles can meet the band gap requirements as much as possible, which is convenient for subsequent applications of perovskite particles.

[0037] In some embodiments, the target band gap is 1 eV to 2 eV. Before fabricating perovskite particles, the applications of the perovskite particles and the requirements of the photoelectric conversion process in solar cells are considered. If the band gap of the perovskite particles is too small, the solar cell fabricated using the perovskite absorber layer constructed from perovskite particles has poor light absorption capacity, absorbing less energy and thus generating a small number of charge carriers, resulting in poor photoelectric conversion efficiency. If the band gap of the perovskite particles is too large, the solar cell fabricated using the absorber layer constructed from perovskite particles cannot absorb low-energy light for photoelectric conversion, reducing the range of light that the solar cell can utilize and leading to a decrease in light utilization efficiency.

[0038] Therefore, the band gap of the perovskite particles to be synthesized is pre-set to be between 1 eV and 2 eV, for example, 1.2 eV, 1.35 eV, 1.5 eV, 1.8 eV, or 1.95 eV, and the perovskite particles are prepared according to the target band gap. By setting the band gap of the perovskite particles to 1 eV to 2 eV, it is easier to subsequently use the perovskite particles to fabricate high-efficiency solar cells, ensuring that the solar cells made using perovskite particles have good photoelectric conversion and light utilization capabilities.

[0039] Step 102: Adjust the reaction conditions of the mixed solution to bring it into the critical state of nucleation of perovskite particles.

[0040] After dissolving the raw materials in the growth mother liquor and mixing them thoroughly to obtain a mixed solution, the particle synthesis equipment adjusts the reaction conditions of the mixed solution to allow the reaction system in the mixed solution to enter the nucleation state of perovskite particles. The reaction conditions include temperature, pressure, and catalyst.

[0041] In some embodiments, adjusting the reaction conditions of the mixed solution includes adjusting the temperature of the mixed solution to 50°C-150°C.

[0042] When adjusting the reaction conditions of the mixed solution, it is necessary to consider the suitable nucleation temperature of perovskite particles, that is, the temperature range within the mixed solution where the number of perovskite particles nucleating is maximized. If the temperature of the mixed solution is too high, the reaction rate may be too fast, leading to aggregation of adjacent perovskite particles after nucleation, thus reducing the yield of perovskite particles. Conversely, if the temperature of the mixed solution is too low, the reaction rate may be too slow, resulting in insufficient or slow nucleation of perovskite particles, making it difficult to increase the production capacity of perovskite particles.

[0043] Therefore, before adjusting the reaction conditions of the mixed solution, the suitable nucleation temperature for different types of single-crystal or polycrystalline perovskite particles is determined based on the structure of the perovskite particles to be synthesized. Then, the particle synthesis equipment determines the specific type and structure of the perovskite particles to be synthesized based on the band gap requirements, and determines the suitable nucleation temperature based on the specific type and structure of the synthesized perovskite particles. Finally, considering the suitable reaction temperatures of each material in the reaction system, the temperature of the mixed solution is adjusted to between 50℃ and 150℃, for example, to 55℃, 65℃, 79℃, 92.5℃, 120℃, 138℃, or 147℃, so that the reaction system of the mixed solution reaches the suitable nucleation temperature of the perovskite particles.

[0044] By adjusting the temperature of the mixed solution to 50℃ to 150℃, the reaction system in the mixed solution enters the suitable temperature for perovskite particle nucleation, thereby enabling as many perovskite particles as possible to nucleate in the mixed solution and increasing the number of synthesized perovskite particles.

[0045] It is worth mentioning that during the process of adjusting the temperature of the mixed solution to 50℃ to 150℃, the mixed solution can be heated using a microwave reactor. Taking heating the mixed solution to 115℃ as an example, after transferring the mixed solution to the microwave reactor, the heating temperature can be directly set to 115℃, and the mixed solution will be heated to 115℃ through the microwave reactor. By directly setting the heating temperature, the mixed solution can reach the suitable nucleation temperature of the perovskite particles as quickly as possible. Alternatively, the mixed solution can be heated to 115℃ using gradient heating. For example, by setting the power of the microwave reactor to 250W, the heating temperature and corresponding heating time can be controlled by gradient heating, sequentially: 75℃-5min, 85℃-5min, 95℃-5min, 105℃-10min, 115℃-5min. Gradient heating avoids side reactions or other abnormal reactions caused by excessively rapid temperature rise during the heating process, ensuring that the mixed solution safely reaches the suitable nucleation temperature of the perovskite particles.

[0046] Furthermore, to further improve the synthesis efficiency of perovskite particles, various basic preparation methods can be combined. For example, when combining the antisolvent gas-assisted method for perovskite particle synthesis, the pressure, concentration, and flow rate of the antisolvent gas need to be adjusted when modifying the reaction conditions to further improve the nucleation efficiency and quantity of perovskite particles. Step 103: The mixed solution that has entered the critical state of nucleation is subjected to ultrasonic pulse stimulation, and perovskite particles are screened out in the mixed solution after a preset time.

[0047] The particle synthesis equipment, after adjusting the reaction conditions to bring the reaction system in the mixed solution to the critical nucleation state of perovskite particles, uses an ultrasonic device to stimulate the mixed solution in the critical nucleation state with ultrasonic pulses. Then, it waits for the reaction system in the mixed solution to react, and after a preset time of ultrasonic pulse stimulation, the generated perovskite particles are screened out from the mixed solution. By applying ultrasonic pulse stimulation to the mixed solution in the critical nucleation state, the extreme reaction conditions such as instantaneously generated high temperature, high pressure, and extremely high cooling rate greatly increase the number of perovskite particles in the mixed solution, facilitating the acquisition of a large number of perovskite particles after the preset time. This significantly improves the synthesis efficiency of perovskite particles, avoiding the limitation of raw material synthesis efficiency on the production of perovskite solar cells, and facilitating the mass production of perovskite solar cells. The synthesized perovskite particles can be either monocrystalline or polycrystalline perovskite particles.

[0048] It is worth mentioning that, before subjecting the mixed solution to ultrasonic pulse stimulation at the nucleation critical state, an appropriate stabilizer or additive can be added to the mixed solution, and the added stabilizer or additive should be thoroughly mixed in the mixed solution. The role of the stabilizer and additive is to control the crystal growth rate during crystal growth, reduce the impact of ultrasonic pulse stimulation on the growth of nucleated perovskite particles, make the obtained perovskite particles as uniform in size as possible, reduce crystal defects on the perovskite particles, and improve the quality of the synthesized perovskite particles. The specific type of stabilizer or additive added can be selected according to the structure and type of perovskite particles, and this application embodiment does not limit this.

[0049] In some embodiments, ultrasonic pulse stimulation of a mixed solution that has entered the nucleation critical state includes: ultrasonic pulse stimulation of the mixed solution that has entered the nucleation critical state using ultrasound with a frequency of 1 Hz to 1 MHz.

[0050] The purpose of ultrasonic pulse stimulation of the mixed solution in particle synthesis equipment is to increase the nucleation rate of perovskite particles in the mixed solution, thereby increasing the quantity of synthesized perovskite particles. While excessively high ultrasonic frequencies can provide sufficient energy to significantly improve the nucleation efficiency and quantity of perovskite particles, excessive energy also greatly increases the aggregation ability between adjacent perovskite particles. This leads to over-aggregation of the formed perovskite particles, changing them from single crystals or regular polycrystalline structures to irregular polycrystalline structures. Therefore, although large-scale perovskite particle nucleation occurs in the mixed solution, the excessive aggregation between adjacent perovskite particles significantly reduces the number of single-crystal or regular polycrystalline perovskite particles produced, resulting in a decrease in the perovskite particle preparation efficiency.

[0051] When the frequency of ultrasound used in ultrasonic pulse stimulation is too low, the energy provided by the ultrasonic pulse stimulation is too low, which cannot effectively provide ideal reaction conditions for the nucleation of perovskite particles. Therefore, the increase in the number of perovskite particles in the mixed solution is limited, and the preparation efficiency of perovskite particles cannot be effectively improved.

[0052] Therefore, during ultrasonic pulse stimulation, the frequency of the ultrasound waves used needs to be controlled. Ultrasonic waves with a frequency of 1 Hz to 1 MHz are used to pulse stimulate the mixed solution that has entered the nucleation critical state. For example, ultrasonic waves with frequencies of 5 Hz, 10 Hz, 75 Hz, 100 Hz, 500 Hz, 1 kHz, 5 kHz, 10 kHz, 100 kHz, 500 kHz, 750 kHz, or 900 kHz can be used to pulse stimulate the mixed solution. This greatly increases the number of perovskite particles nucleated in the mixed solution while preventing excessive aggregation between adjacent perovskite particles. This transforms the monocrystalline or regular polycrystalline perovskite particles to be synthesized into irregular polycrystalline particles, ensuring a significant increase in the actual yield of perovskite particles.

[0053] In some embodiments, the duration of the ultrasonic pulse stimulation is from 0.001 s to 1 s.

[0054] In particle synthesis equipment, the number of perovskite particles nucleated in a mixed solution is affected not only by the energy carried by the ultrasound waves but also by the duration of the ultrasound pulse stimulation. If the ultrasound pulse stimulation is too long, some perovskite particles may grow too rapidly after nucleation, leading to adhesion or aggregation between adjacent particles. This can cause single-crystal perovskite particles to aggregate into polycrystalline perovskite particles, or regular polycrystalline perovskite particles to transform into irregular polycrystalline perovskite particles. Furthermore, continuous ultrasound pulse stimulation can significantly increase crystal defects on the perovskite particles, affecting the quality of the formed perovskite particles.

[0055] When the duration of ultrasonic pulse stimulation is too short, the number of perovskite particles that can rapidly nucleate is limited. The nucleation process of some perovskite particles may be interrupted, entering a slow nucleation phase or failing to nucleate at all, resulting in a limited increase in the number of nucleated perovskite particles. Simultaneously, due to the short duration of ultrasonic pulse stimulation, the growth rate of nucleated perovskite particles is also relatively slow. The time required for nucleated perovskite particles to grow to a sufficient size is significantly increased, thus greatly increasing the waiting time required for screening perovskite particles and limiting the efficiency of perovskite particle preparation.

[0056] Therefore, during ultrasonic pulse stimulation, the duration of the ultrasonic pulse stimulation needs to be controlled, specifically between 0.001 s and 1 s for the mixed solution entering the nucleation critical state. For example, the duration can be controlled at 0.001 s, 0.002 s, 0.005 s, 0.01 s, 0.015 s, 0.025 s, 0.05 s, 0.08 s, 0.1 s, 0.2 s, 0.5 s, or 0.75 s. This significantly increases the number of perovskite particles nucleated in the mixed solution, reduces the preset waiting time for perovskite particle screening, and prevents adhesion or aggregation between perovskite particles, ensuring the quantity of final perovskite particles generated and minimizing crystal defects, thus guaranteeing the quality of the perovskite particles.

[0057] Furthermore, by controlling both the duration of the ultrasonic pulse stimulation and the frequency of the ultrasonic waves used during the ultrasonic pulse stimulation process, the mixed solution can be stimulated for an appropriate duration using suitable ultrasonic waves. This maximizes the number of perovskite particles that can nucleate, while preventing the aggregation of perovskite particles during growth, ensuring the quality of the perovskite particles, and maximizing the production capacity of perovskite particles.

[0058] In some embodiments, after subjecting the mixed solution to ultrasonic pulse stimulation that has entered the nucleation critical state, the method further includes: adjusting the temperature of the mixed solution to 25°C-150°C.

[0059] After ultrasonic pulse stimulation of the mixed solution, the particle synthesis equipment causes a large number of perovskite particles to nucleate in the solution. These nucleated perovskite particles then grow within the solution. During growth, if the temperature of the mixed solution is too high, the particle growth rate may be excessive, leading to adhesion or aggregation between adjacent particles, resulting in a decrease in the final number of perovskite particles. Conversely, if the temperature is too low, the particle growth rate may be too low, resulting in slow particle growth and a longer pre-set waiting time for perovskite particle screening, thus limiting the perovskite particle production capacity.

[0060] Therefore, after ultrasonic pulse stimulation, the temperature of the mixed solution is adjusted to between 25°C and 150°C, for example, to 25°C, 30°C, 35°C, 45°C, 55°C, 65°C, 79°C, 92.5°C, 120°C, 138°C, or 147°C, so that the reaction system of the mixed solution enters the growth temperature suitable for perovskite particles. This allows the growth of perovskite particles after nucleation in the mixed solution to be as rapid as possible, while avoiding aggregation or adhesion between adjacent perovskite particles, thereby increasing the number of synthesized perovskite particles.

[0061] Furthermore, the suitable nucleation temperature and suitable growth temperature of perovskite particles may be the same or different, depending on the structure and type of the perovskite particles. Therefore, whether to adjust the temperature of the mixed solution after ultrasonic pulse stimulation can be determined according to the type and structure of the perovskite particles to be synthesized. This application does not limit this.

[0062] In some embodiments, screening perovskite particles in a mixed solution after a preset time period includes: screening target perovskite particles in a mixed solution, wherein the maximum distance between any two points on the outer surface of the target perovskite particles is 5 micrometers to 100 micrometers.

[0063] In the process of screening perovskite particles from a mixed solution after a preset time in the particle synthesis equipment, the perovskite particles formed in the mixed solution can first be scooped out by a robotic arm and transferred to an intermediate container. Then, the perovskite particles in the intermediate container are rinsed clean and transferred to a screening machine to screen out the target perovskite particles of suitable size as the product.

[0064] When the size of perovskite particles is too large—that is, the maximum distance between any two points on the particle surface is too large—after the absorber layer of a solar cell is made from perovskite particles, the distance that charge carriers need to travel to migrate to the carrier transport layer or conductive layer after absorbing light energy is too great, making carrier migration difficult and resulting in poor photoelectric conversion efficiency of the solar cell. Conversely, when the size of perovskite particles is too small—that is, the maximum distance between any two points on the particle surface is too small—the spacing between different charge carriers is very small during migration, making carrier recombination more likely and also leading to poor photoelectric conversion efficiency of the solar cell.

[0065] Therefore, in the screening process of perovskite particles, target perovskite particles with a maximum distance of 5-100 micrometers between any two points on the particle surface are selected. For example, target perovskite particles with a maximum distance of 5 μm, 7.5 μm, 10 μm, 15 μm, 25 μm, 60 μm, 80 μm, 85 μm, or 95 μm between any two points on the particle surface are selected as the synthesis products. This ensures that charge carriers can migrate relatively easily while reducing the probability of recombination between different charge carriers, thereby maximizing the photoelectric conversion efficiency of solar cells made using perovskite particles.

[0066] Furthermore, during the screening of target perovskite particles, a screening machine can be used to first remove particles smaller than 5 μm, and then remove particles larger than 100 μm; alternatively, particles larger than 100 μm can be removed first, followed by particles smaller than 5 μm, where the particle size is the maximum distance between any two points on the particle surface. This application does not limit the specific screening method.

[0067] Furthermore, during the screening of target perovskite particles, for the convenience of subsequent utilization of the perovskite particles, further screening may be performed on particles with specific sizes within the target perovskite particles. For example, in the process of preparing single-particle perovskite film using perovskite particles, perovskite particles with a size of 80μm to 85μm have better film-forming effects. Therefore, in the screening of target perovskite particles, target perovskite particles with a size of 5μm to 100μm can be screened first, and then perovskite particles with a size of 80μm to 85μm can be screened from the target perovskite particles. Alternatively, in the screening process, the size of the target perovskite particles can be directly limited to 80μm to 85μm, and perovskite particles with a size of 80μm to 85μm can be screened out as target perovskite particles using a sieve machine. The specific screening method in the screening process is the same as the method for screening target perovskite particles with a size of 5μm to 100μm, and will not be repeated here. By further screening the target perovskite particles or further limiting the size range of the target perovskite particles, the target perovskite particles that are easy to use can be accurately screened from the mixed solution, thereby improving the ease of application of perovskite particles.

[0068] In some embodiments, the preset time is 1 min to 2 h. Before screening the target perovskite particles, it is necessary to wait for the particles to grow in the mixed solution for a preset time. If the preset time is too short, the particle growth time is limited, and the size of the screened particles is too small; if the preset time is too long, the particle growth time is too long, and the size of the screened particles is too large.

[0069] Therefore, before screening the target perovskite particles in the particle synthesis equipment, the preset time for perovskite particle generation should be set to a duration between 1 minute and 2 hours, for example, 1 minute, 5 minutes, 20 minutes, 45 minutes, 1 hour, 1.5 hours, or 110 minutes. This ensures an appropriate growth time for the perovskite particles in the mixed solution and maximizes the number of target perovskite particles in the mixed solution, thereby improving the production capacity of the target perovskite particles.

[0070] Furthermore, due to the inherent error in the nucleation time of each perovskite particle in the mixed solution, and the unavoidable interference of ultrasonic pulse stimulation in the formation of some perovskite particles, the distribution of perovskite particles of different sizes in the mixed solution can be approximated as a normal distribution. Therefore, by setting a specific preset time based on the target size of the target perovskite particles—that is, the target range of the maximum distance between any two points on the particle surface—the number of perovskite particles of the target size in the mixed solution can be maximized. This further improves the synthesis efficiency and production capacity of the target perovskite particles.

[0071] In some embodiments, after screening out the target perovskite particles, the method further includes: redissolving the remaining particles other than the target perovskite particles in the growth mother liquor or mixed solution.

[0072] After screening out the target perovskite particles, the particle synthesis equipment redissolves any oversized or undersized particles in the growth mother liquor as raw materials for subsequent perovskite particle synthesis, avoiding waste and reducing the cost of perovskite particle synthesis. Alternatively, oversized or undersized particles can be redissolved in a mixed solution, and the reaction conditions of the mixed solution can be readjusted for secondary perovskite particle preparation, avoiding waste of remaining raw materials and particles in the mixed solution and further reducing the cost of perovskite particle synthesis.

[0073] In summary, the perovskite particle preparation method provided in one embodiment of this application involves adjusting the reaction conditions of the mixed solution after dissolving the raw materials in the growth mother liquor and mixing them thoroughly to obtain a mixed solution. This adjusts the reaction system in the mixed solution to the critical nucleation state of the perovskite particles. By adjusting the reaction system in the mixed solution to the critical nucleation state of the perovskite particles, the difficulty and time required for perovskite particle nucleation are reduced, thereby improving the nucleation efficiency and probability of perovskite particles. Then, the mixed solution in the critical nucleation state is subjected to ultrasonic pulse stimulation, and perovskite particles are screened out from the mixed solution after a preset time. By applying ultrasonic pulse stimulation to the mixed solution in the critical nucleation state, the extreme reaction conditions such as instantaneously generated high temperature, high pressure, and extremely high cooling rate greatly increase the number of perovskite particles in the mixed solution, making it easier to obtain a large number of perovskite particles after a preset time. This significantly improves the synthesis efficiency of perovskite particles, avoids the constraint of raw material synthesis efficiency on the production of perovskite solar cells, and facilitates the mass production of perovskite solar cells.

[0074] Accordingly, another embodiment of this application also provides a solar cell, the structural schematic diagram of which can be referred to. Figure 2 It includes: a first conductive layer 201, a first carrier transport layer 202, a perovskite absorption layer 203, and a second conductive layer 204, which are stacked sequentially. The perovskite absorption layer includes a plurality of perovskite particles, which are formed by the perovskite particle preparation method described above.

[0075] The first conductive layer 201 and the second conductive layer 204 can be composed of metal grid lines or conductive thin films, and are used to transmit the electrical energy generated by the solar cell to external components.

[0076] In some embodiments, the first carrier transport layer 202 is a hole transport layer or an electron transport layer.

[0077] That is, the function of the first carrier transport layer 202 is to collect and transport the carriers generated in the perovskite absorber layer 203. Based on the working mechanism of the solar cell, the first carrier transport layer 202 can be either a hole transport layer or an electron transport layer.

[0078] refer to Figure 3 In some embodiments, the solar cell further includes a second carrier transport layer 205, which is located between the perovskite absorber layer 203 and the second conductive layer 204, and is in contact with the perovskite absorber layer 203 and the second conductive layer 204, respectively.

[0079] To further improve the efficiency of solar cells, carrier transport layers for collecting and transporting different carriers can be set on opposite sides of the perovskite absorber layer 203.

[0080] In some embodiments, when the first carrier transport layer 202 is a hole transport layer, the second carrier transport layer 205 is an electron transport layer; when the first carrier transport layer 202 is an electron transport layer, the second carrier transport layer 205 is a hole transport layer.

[0081] Accordingly, another embodiment of this application also provides a tandem solar cell, the structural schematic diagram of which can be referred to. Figure 4 It includes: a top cell 401, an adhesive layer 402 and a bottom cell 403 stacked in sequence, wherein the top cell 401 is the aforementioned solar cell.

[0082] In some embodiments, the type of the bottom cell 403 includes crystalline silicon solar cells, CIGS thin-film solar cells, cadmium telluride thin-film solar cells, III-V thin-film solar cells, or narrow bandgap perovskite thin-film solar cells, wherein the narrow bandgap perovskite thin-film solar cells can be narrow bandgap monocrystalline perovskite thin-film solar cells or narrow bandgap polycrystalline perovskite thin-film solar cells.

[0083] In some embodiments, the bonding layer 402 includes a mechanical bonding layer engineered with conductive adhesive. The conductive adhesive can be formed by adding conductive particles to a transparent adhesive with good light transmittance, for example, by adding conductive particles to an adhesive with transmittance of 80% or more for light above 400 nm or above, or an adhesive with transmittance of 80% or more for light above 450 nm. The conductive adhesive can also be a transparent thin adhesive whose constituent particles have a certain degree of conductivity; the degree of transparency can be similar to that of the aforementioned adhesives, and will not be further elaborated upon. This application does not limit the specific type of conductive adhesive.

[0084] Although this application discloses preferred embodiments as described above, it is not intended to limit the claims. Any person skilled in the art can make several possible changes and modifications without departing from the concept of this application. Therefore, the scope of protection of this application should be determined by the scope defined in the claims of this application.

[0085] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A method for preparing perovskite particles, characterized by, include: Organic and inorganic raw materials are dissolved in the growth mother liquor and mixed evenly to obtain a mixed solution; After adjusting the reaction conditions of the mixed solution, ultrasonic pulse stimulation is performed, and the perovskite particles are screened out from the mixed solution after a preset time.

2. The method for preparing perovskite particles according to claim 1, characterized in that, The ultrasonic pulse stimulation includes: The mixed solution, after its reaction conditions have been adjusted, is subjected to ultrasonic pulse stimulation using ultrasound with a frequency of 1 Hz to 1 MHz.

3. The method for preparing perovskite particles according to claim 1, characterized in that, The duration of the ultrasonic pulse stimulation is from 0.001 s to 1 s.

4. The method for preparing perovskite particles according to claim 1, characterized in that, The step of screening the perovskite particles in the mixed solution after a preset time period includes: The target perovskite particles are screened out in the mixed solution, and the maximum distance between any two points on the outer surface of the target perovskite particles is 5 micrometers to 100 micrometers.

5. The method for preparing perovskite particles according to claim 4, characterized in that, After screening out the target perovskite particles, the method further includes: redissolving the remaining particles other than the target perovskite particles in the growth mother liquor or the mixed solution.

6. The method for preparing perovskite particles according to claim 1, characterized in that, The preset duration is from 1 minute to 2 hours.

7. The method for preparing perovskite particles according to claim 1, characterized in that, Adjusting the reaction conditions of the mixed solution includes adjusting the temperature of the mixed solution.

8. The method for preparing perovskite particles according to claim 7, characterized in that, The adjustment of the reaction conditions of the mixed solution includes adjusting the temperature of the mixed solution to 50℃-150℃.

9. The method for preparing perovskite particles according to claim 8, characterized in that, The temperature of the mixed solution was adjusted to 115°C.

10. The method for preparing perovskite particles according to claim 9, characterized in that, The method for adjusting the temperature of the mixed solution includes a gradient heating method, specifically: heating at 75°C for 5 minutes, heating at 85°C for 5 minutes, heating at 95°C for 5 minutes, heating at 105°C for 10 minutes, and heating at 115°C for 5 minutes.

11. The method for preparing perovskite particles according to claim 1, characterized in that, After adjusting the reaction conditions of the mixed solution and before performing ultrasonic pulse stimulation, the method further includes adding a stabilizer or additive to the mixed solution.

12. The method for preparing perovskite particles according to claim 1, characterized in that, After the mixed solution is subjected to ultrasonic pulse stimulation following adjustment of the reaction conditions, the method further includes: adjusting the temperature of the mixed solution to 25℃-150℃.

13. The method for preparing perovskite particles according to any one of claims 1 to 12, characterized in that, Before dissolving the organic and inorganic raw materials in the growth mother liquor, the method further includes: The molar mass ratio of each element in the perovskite particle is determined based on the target band gap of the perovskite particle. The organic raw material and the inorganic raw material are weighed according to the molar mass ratio of each element in the perovskite particles.

14. The method for preparing perovskite particles according to claim 13, characterized in that, The target band gap is 1 eV to 2 eV.

15. A solar cell, characterized in that, include: A first conductive layer, a first carrier transport layer, a perovskite absorption layer, and a second conductive layer are sequentially stacked. The perovskite absorption layer includes a plurality of perovskite particles, which are formed by the perovskite particle preparation method as described in any one of claims 1 to 14.

16. The solar cell according to claim 15, characterized in that, The first carrier transport layer is either a hole transport layer or an electron transport layer.

17. The solar cell according to claim 15, characterized in that, Also includes: The second carrier transport layer is located between the perovskite absorber layer and the second conductive layer, and is in contact with both the perovskite absorber layer and the second conductive layer.

18. The solar cell according to claim 17, characterized in that, When the first carrier transport layer is a hole transport layer, the second carrier transport layer is an electron transport layer; When the first carrier transport layer is an electron transport layer, the second carrier transport layer is a hole transport layer.

19. A tandem solar cell, characterized in that, include: A top cell, an adhesive layer, and a bottom cell are stacked in sequence, wherein the top cell is a solar cell as described in any one of claims 15 to 18.

20. The tandem solar cell according to claim 19, characterized in that, The base cell includes crystalline silicon solar cells, CIGS thin-film solar cells, cadmium telluride thin-film solar cells, III-V thin-film solar cells, or narrow bandgap perovskite thin-film solar cells.

21. The tandem solar cell according to claim 19, characterized in that, The bonding layer includes a mechanical bonding layer made of conductive adhesive.

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