In-situ preparation method of two-dimensional pure iodine perovskite nanocrystalline applied to fluorescent condenser

Abstract

The invention discloses an in-situ preparation method of two-dimensional pure iodine perovskite nanocrystals applied to a fluorescent condenser. The in-situ preparation method comprises four steps of precursor-polymer matrix preparation, liquid-phase thermal injection induced nucleation, gas-phase assisted crystallization and dimension regulation and control, and post-treatment and device assembly. An in-situ growth strategy is adopted, liquid-phase thermal injection and gas-phase auxiliary crystallization are combined, the problem of nanocrystalline agglomeration is solved, precise regulation and control of a two-dimensional structure are achieved, and the crystallinity and stability of the material are improved. The process is simplified, the controllability is high, the energy consumption is low, the prepared composite material is adaptive to multiple types of photovoltaic cells, the efficiency of a fluorescent condenser can be improved, the cost is reduced, the industrialization of the fluorescent condenser is promoted, and the composite material is suitable for the field of photovoltaic energy.

Description

Technical Field

[0001] This invention relates to the field of perovskite material preparation technology, specifically to an in-situ method for preparing two-dimensional pure iodine perovskite nanocrystals for use in fluorescent concentrators. Background Technology

[0002] As a novel light-collecting and conversion device, fluorescent concentrators can efficiently capture and concentrate large areas of sunlight onto edge photovoltaic cells, effectively reducing the cost of photovoltaic systems and improving energy efficiency. They have significant application value in building-integrated photovoltaics (BIPV), portable energy devices, and other fields. The performance of the core waveguide layer material is a key factor determining the efficiency of fluorescent concentrator devices. Ideal waveguide layer materials need to possess broad-spectrum absorption, high fluorescence quantum yield, good photostability, and excellent optical transparency.

[0003] Perovskite materials have become a research hotspot for core materials in fluorescent concentrators due to their unique optoelectronic properties, such as tunable band gaps, high light absorption coefficients, and fluorescence quantum yields. Among them, pure iodine perovskite materials have band gaps suitable for solar light absorption, and iodine is abundant and inexpensive, showing great potential in fluorescent concentrator applications. However, three-dimensional pure iodine perovskite materials suffer from poor chemical stability, easy aggregation, and poor dispersibility in polymer matrices, which limits their practical applications.

[0004] Two-dimensional perovskite materials, by introducing long-chain organic cations to form a layered structure, can effectively improve the chemical stability and environmental tolerance of the materials, while their quantum confinement effect can further optimize optical performance. Currently, the preparation methods for two-dimensional perovskite nanocrystals mainly include solution methods, hot-injection methods, and mechanical exfoliation methods. However, most of these methods require the preparation of nanocrystalline powder first, followed by mixing with a polymer matrix. This process is prone to nanocrystal agglomeration and uneven dispersion, affecting the optical performance of the composite material and the stability of the device. Furthermore, existing methods struggle to precisely control the dimensions and size of two-dimensional perovskite nanocrystals, resulting in poor material performance consistency and hindering large-scale production.

[0005] Therefore, developing a preparation method that enables the in-situ growth of two-dimensional pure iodine perovskite nanocrystals in a polymer matrix and allows for precise control of the nanocrystal structure and properties is of great significance for promoting the industrial application of fluorescent concentrators. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of poor dispersibility, difficulty in structure control, and complex processes in the preparation of two-dimensional pure iodine perovskite nanocrystals in existing technologies, and to provide an in-situ preparation method for two-dimensional pure iodine perovskite nanocrystals for fluorescent concentrators. This method achieves uniform dispersion of nanocrystals in a polymer matrix through an in-situ growth strategy, and combines liquid-phase thermal injection and gas-phase assisted crystallization to precisely control the two-dimensional structure and size of the nanocrystals, thus preparing a high-performance composite material and providing a high-quality core material for fluorescent concentrator devices.

[0007] To achieve the above objectives, the present invention employs the following technical means:

[0008] An in-situ preparation method for two-dimensional pure iodine perovskite nanocrystals for fluorescent concentrator applications includes the following steps:

[0009] Step 1, Preparation of precursor-polymer matrix:

[0010] Cesium source, lead source, and organic long-chain ammonium salt are dissolved in a strongly polar aprotic solvent in stoichiometric ratio to form a perovskite precursor solution; a transparent polymer matrix is ​​dissolved in the perovskite precursor solution and stirred thoroughly to obtain a uniform and transparent mixed slurry; the mixed slurry is then formed into a wet film or a preform of a specific shape by spin coating, blade coating, or casting.

[0011] Step 2: Liquid-phase thermal injection to induce nucleation:

[0012] The wet film or preform containing the precursor obtained in step 1 is transferred to a heating platform and subjected to rapid heating under an inert atmosphere. The temperature is raised to a specific temperature and held for a short time to allow the solvent to evaporate rapidly. The precursor reaches a supersaturated state in the polymer network and rapidly nucleates to form initial nanocrystal nuclei.

[0013] Step 3: Vapor-assisted crystallization and dimensional control:

[0014] A gaseous environment containing organic amine vapor was prepared by mixing a weakly polar solvent with an appropriate amount of organic amine and placing the mixture at the bottom of a sealed container. The sample treated in step 2 was suspended in the sealed container without contact with the liquid. The entire sealed container was heated at a low temperature for a period of time to allow the organic amine vapor to diffuse and penetrate into the polymer matrix, where it coordinates with the lead-iodine octahedrons in the initial nanocrystal nuclei, promoting the directional growth and crystallinity of the two-dimensional layered structure, while simultaneously controlling the thickness of the nanosheets.

[0015] Step 4, Post-processing and Device Assembly:

[0016] The sample processed in step 3 was taken out of the gas phase environment and annealed to remove residual solvent. After cooling to room temperature, a transparent polymer composite material thin plate with uniformly dispersed two-dimensional pure iodine perovskite nanocrystals was obtained. The composite material thin plate was used as the core waveguide layer, and silicon photovoltaic cells or other types of photovoltaic cells were coupled at its edge to assemble a fluorescent concentrator device.

[0017] Preferably, in step 1, the cesium source is at least one of cesium carbonate, cesium nitrate, cesium chloride, or cesium iodide; the lead source is at least one of lead iodide, lead nitrate, lead acetate, or lead chloride; the organic long-chain ammonium salt is at least one of n-butylammonium iodide, n-octylammonium iodide, dodecylammonium iodide, or hexadecylammonium iodide; and the stoichiometric ratio of the cesium source, lead source, and organic long-chain ammonium salt is 1:(1-1.2):(0.8-1.2).

[0018] Preferably, in step 1, the strongly polar aprotic solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, or hexamethylphosphoramide; the transparent polymer matrix is ​​at least one of polymethyl methacrylate, polystyrene, polycarbonate, or polyvinyl chloride; and the mass fraction of the polymer matrix in the mixed slurry is 5%-20%.

[0019] Preferably, in step 1, the spin coating speed is 1000-5000 r / min and the spin coating time is 30-180 s; the wet film thickness of the scraper coating is 50-500 μm; the shape of the cast preform is set according to the requirements of the fluorescent concentrator device, including rectangular, circular or trapezoidal shapes.

[0020] Preferably, in step 2, the inert atmosphere is nitrogen or argon; the rapid heating rate is 10-50℃ / min; the specific temperature is 80-150℃, and the holding time is 5-30min.

[0021] Preferably, in step 3, the weakly polar poor solvent is at least one of toluene, benzene, xylene or chlorobenzene; the organic amine is at least one of methylamine, ethylamine, propylamine or butylamine; and the volume ratio of the organic amine to the weakly polar poor solvent is 1:(5-20).

[0022] Preferably, in step 3, the lower temperature is 40-80℃ and the heating time is 1-6h.

[0023] Preferably, in step 4, the annealing temperature is 60-120℃ and the annealing time is 0.5-3h; the thickness of the composite material sheet is 100-1000μm.

[0024] Preferably, in step 4, the other types of photovoltaic cells are cadmium telluride photovoltaic cells, copper indium gallium selenide photovoltaic cells, or perovskite photovoltaic cells.

[0025] The present invention has the following beneficial effects:

[0026] 1. Material properties: Achieving synergistic optimization of "high uniformity + high crystallinity + directional structure" in two-dimensional nanocrystals

[0027] Solving the problem of nanocrystal agglomeration and dispersion: Unlike the traditional process of "preparing nanocrystal powder first and then mixing polymer", this invention adopts an in-situ growth strategy. The precursor molecules are uniformly dispersed in the polymer solution. Under the confinement of the polymer network, the initial nanocrystal nuclei are difficult to agglomerate freely. The resulting two-dimensional pure iodine perovskite nanocrystals have significantly improved dispersion uniformity in the polymer matrix, avoiding fluctuations in optical performance caused by uneven dispersion.

[0028] Precise control of two-dimensional structure and crystal quality: The rapid heating process of liquid-phase thermal injection promotes rapid supersaturation nucleation of the precursor, laying the foundation for the two-dimensional structure; the subsequent gas-phase assisted crystallization guides the crystal to grow in a two-dimensional direction through the coordination of organic amine vapor and lead-iodine octahedrons, forming a layered structure with controllable thickness, which meets the precise requirements of the fluorescence concentrator for the quantum confinement effect of the material; on the other hand, it reduces the crystal growth activation energy, reduces defect sites, improves the crystallinity of nanocrystals, and ensures high fluorescence quantum yield.

[0029] Enhancing material stability and compatibility: The "isolation layer" formed by organic long-chain ammonium salts in the two-dimensional layered structure effectively prevents external water vapor and oxygen from eroding the perovskite core structure, significantly improving chemical stability compared to three-dimensional pure iodine perovskite materials; at the same time, the transparent polymer matrix and nanocrystals have excellent interfacial compatibility, and the composite material has high visible light transmittance, meeting the core requirements of "high transparency + low light loss" for the waveguide layer of fluorescent concentrators.

[0030] 2. Process Innovation: Achieving a breakthrough in processes characterized by "low complexity + high controllability + scalability adaptation".

[0031] Simplified process flow and reduced operation difficulty: Integrating multiple steps of "nucleation-crystallization-composite" into one, eliminating the need for additional nanocrystal purification and dispersion treatment, greatly reducing process steps; Spin coating, scraping coating, casting and other film-forming methods can flexibly adapt to preforms of different shapes, without the need for complex molds or special equipment, and can be quickly adapted to ordinary laboratories and industrial production lines.

[0032] Key parameters can be precisely controlled, with excellent repeatability: By controlling parameters such as precursor stoichiometry, liquid phase thermal injection rate, and gas phase organic amine concentration, the nanocrystal size and composite material sheet thickness can be precisely adjusted, and the material performance deviation between different batches is small, solving the industry pain point of "parameter sensitivity and poor repeatability" in traditional processes.

[0033] Balancing low energy consumption with safety and environmental protection: The nucleation temperature of liquid phase thermal injection, the crystallization temperature of gas phase assisted crystallization, and the annealing temperature are all in the medium and low temperature range, which significantly reduces energy consumption compared with the high temperature solid phase method; the entire process is protected by an inert atmosphere to avoid perovskite oxidation, and the weakly polar solvent can be recovered through a sealed container to improve solvent utilization and reduce environmental pollution.

[0034] 3. Device Applications: Enabling the Upgrade of Fluorescent Concentrators to Achieve "High Efficiency + Low Cost + Wide Range of Applications"

[0035] Improving the energy conversion efficiency of fluorescent concentrators: The composite material thin plate prepared in this invention serves as the core waveguide layer, possessing both "broad spectrum absorption + high fluorescence directional transmission" characteristics. Through total internal reflection, it concentrates large-area sunlight onto the edge photovoltaic cells, significantly improving light collection efficiency compared to traditional glass-based waveguide layers. It also exhibits excellent compatibility with silicon photovoltaic cells, cadmium telluride photovoltaic cells, etc., and can be flexibly adapted to different types of photovoltaic devices, broadening application scenarios.

[0036] Reduce photovoltaic system costs: Fluorescent concentrators can reduce the amount of photovoltaic cells used by combining "small-area photovoltaic cells + large-area waveguide layers", thus significantly reducing system costs. At the same time, the process of this invention does not require expensive equipment, the raw materials are abundant, and the cost of composite materials per unit area is lower than that of traditional perovskite-polymer composite systems when mass-produced.

[0037] Adaptable to diverse application scenarios: The composite material thin sheet has excellent mechanical properties and can be made into flexible or irregular structures to meet the needs of scenarios such as building-integrated photovoltaics and portable energy equipment, breaking through the application limitations of traditional rigid fluorescent concentrators.

[0038] 4. Technological barriers: Building core technological advantages through "in-situ growth + gas-phase control"

[0039] This invention innovatively combines "liquid-phase thermal injection nucleation" with "gas-phase assisted crystallization" to form a unique "two-step dimensional control" technical route: the first step rapidly locks the two-dimensional nucleation trend through liquid-phase thermal injection, avoiding three-dimensional growth; the second step achieves precise control of crystallinity and thickness through slow gas-phase infiltration. This technical route is difficult to replicate by traditional solution methods or mechanical exfoliation methods, forming a significant technical barrier. Simultaneously, the synergistic mechanism of polymer network confinement and organic amine coordination in the process provides a generalizable technical framework for the in-situ preparation of other two-dimensional perovskite materials.

[0040] 5. Industrialization Value: Driving the perovskite fluorescent concentrator from the laboratory to industrialization

[0041] Adaptable to large-scale production needs: The process steps are simple and controllable. Film-making methods such as spin coating and scraping coating can be continuously produced through roll-to-roll equipment, and the capacity of a single production line is considerable. The shape of the preform can be flexibly adjusted according to order requirements without redesigning the production line, which meets the industrialized "multi-variety + large-volume" production mode.

[0042] Lowering the barriers to technology implementation: The process has mild requirements for the operating environment and does not require special equipment such as ultra-high vacuum or anhydrous and oxygen-free glove boxes. The equipment investment cost is low, and small and medium-sized enterprises can quickly enter the market. At the same time, the specific parameters provided in the examples can be directly used as the benchmark scheme for industrial production, shortening the technology transformation cycle. Detailed Implementation

[0043] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] A method for in-situ preparation of two-dimensional pure iodine perovskite nanocrystals for use in fluorescent concentrators includes the following steps:

[0045] 1. Preparation of precursor-polymer matrix

[0046] First, prepare cesium source, lead source, and organic long-chain ammonium salt according to the stoichiometric ratio. The cesium source is selected from compounds that are easily soluble in strongly polar aprotic solvents, such as cesium carbonate, cesium nitrate, cesium chloride, or cesium iodide. The lead source is selected from lead-containing compounds such as lead iodide and lead nitrate, with lead iodide being preferred to reduce the introduction of impurity ions. The organic long-chain ammonium salt is selected from compounds such as n-butylammonium iodide and n-octylammonium iodide, whose long-chain structure can help form a two-dimensional layered structure. The stoichiometric ratio of cesium source, lead source, and organic long-chain ammonium salt is controlled at 1:(1-1.2):(0.8-1.2) to ensure an appropriate proportion of precursor components, providing a good foundation for subsequent nanocrystal growth.

[0047] The above-mentioned raw materials are dissolved in a highly polar aprotic solvent, such as N,N-dimethylformamide or dimethyl sulfoxide. These solvents have high polarity and good solubility, enabling the precursors to dissolve fully and form a homogeneous perovskite precursor solution. Subsequently, a transparent polymer matrix (such as polymethyl methacrylate or polystyrene) is dissolved in this precursor solution. The mass fraction of the polymer matrix is ​​controlled between 5% and 20%. Too low a mass fraction will result in insufficient mechanical properties of the subsequently formed composite material, while too high a mass fraction will affect the diffusion and nucleation of the precursor. The polymer matrix is ​​completely dissolved by magnetic or mechanical stirring (stirring rate of 300-800 r / min, stirring time of 2-6 h), forming a homogeneous and transparent mixed slurry. At this point, the precursor molecules are uniformly dispersed in the polymer solution, laying the foundation for in-situ nucleation.

[0048] Finally, depending on the required shape and size of the fluorescent concentrator, the mixed slurry is prepared into a wet film or a preform of a specific shape using spin coating, blade coating, or casting. During spin coating, the rotation speed is set to 1000-5000 r / min. Too low a speed will result in an excessively thick wet film and uneven solvent evaporation, while too high a speed will result in an excessively thin wet film, affecting the subsequent growth of nanocrystals. The spin coating time is controlled between 30-180 s. During blade coating, the wet film thickness is controlled to be 50-500 μm by adjusting the blade gap. Casting involves pouring the mixed slurry into a custom mold to form a preform of a specific shape, such as a rectangle, circle, or trapezoid, to meet the structural requirements of different devices.

[0049] 2. Liquid-phase thermal injection-induced nucleation

[0050] The wet film or preform containing the precursor prepared in step 1 is rapidly transferred to a heating platform. To prevent the precursor from being oxidized or moistened in air, the entire process must be carried out under an inert atmosphere (nitrogen or argon). The heating platform is then turned on, and the temperature is increased rapidly at a rate of 10-50℃ / min. This rapid heating causes the solvent to evaporate quickly, allowing the precursor to rapidly reach a supersaturated state within the polymer network, thus triggering the nucleation process. When the temperature reaches 80-150℃, it is maintained for 5-30 minutes. During this stage, the solvent continues to evaporate, and the precursor molecules continuously aggregate. Under the confinement of the polymer network, free growth in the three-dimensional direction is difficult, and nucleation preferentially occurs in the two-dimensional direction, forming the initial nanocrystal nuclei. The spatial hindrance of the polymer chains effectively inhibits the aggregation of nanocrystals and provides a supporting framework for the subsequent directional growth of the two-dimensional structure.

[0051] 3. Vapor-assisted crystallization and dimensional control

[0052] To further refine the two-dimensional structure of nanocrystals, increase crystallinity, and precisely control the thickness of nanosheets, vapor-phase assisted crystallization is required. First, a vapor environment containing organic amine vapor is prepared: a weakly polar solvent (such as toluene, benzene, or xylene) is added to the bottom of a sealed container (such as a PTFE reactor or a glass sealed jar). These solvents have poor compatibility with the polymer matrix, preventing solvent penetration that could lead to polymer swelling. Simultaneously, an appropriate amount of organic amine (such as methylamine, ethylamine, or propylamine) is added. The volume ratio of organic amine to the weakly polar solvent is controlled at 1:(5-20). A volume ratio that is too high will result in an excessively high concentration of organic amine, causing excessive nanocrystal growth; a volume ratio that is too low will not effectively promote crystallization.

[0053] The nucleated sample from step 2 is suspended in a sealed container, ensuring it does not directly contact the liquid at the bottom to prevent corrosion or dissolution of the sample surface. The entire sealed container is placed in a constant temperature environment of 40-80℃ (an oven or a constant temperature water bath can be used) and heated for 1-6 hours. During heating, the organic amine and the weakly polar solvent co-evaporate, forming an organic amine vapor atmosphere. The organic amine vapor slowly diffuses and penetrates into the polymer matrix. The amino groups in the organic amine molecules can coordinate with the lead-iodine octahedrons in the initial nanocrystal nuclei. On the one hand, this guides the lead-iodine octahedrons to align in a two-dimensional direction, promoting the growth of a two-dimensional layered structure. On the other hand, the coordination effect can lower the activation energy for crystal growth, increase the crystallinity of the nanocrystals, and reduce crystal defects. Simultaneously, by controlling the organic amine vapor concentration (i.e., the volume ratio of organic amine to the poor solvent) and the heating time, the thickness of the nanosheets can be precisely controlled within the range of 5-20 nm, meeting the optical performance requirements of the fluorescent concentrator. The slow diffusion characteristics of the gas phase environment ensure that the organic amine is uniformly distributed in the polymer matrix, thereby making the nanocrystals uniform in size (particle size distribution deviation less than 10%) and uniformly dispersed, avoiding the problem of nanocrystal agglomeration in the traditional solution method.

[0054] 4. Post-processing and device assembly

[0055] After removing the sample from the sealed container following vapor-phase assisted crystallization in step 3, trace amounts of weakly polar solvents and unreacted organic amines may still remain. These residues can affect the optical transparency and stability of the composite material, necessitating annealing. Place the sample in an oven and anneal at 60-120°C for 0.5-3 hours. Annealing at too low a temperature or for too short a time will not completely remove the residual solvent, while annealing at too high a temperature or for too long may damage the nanocrystalline structure. Annealing allows the residual solvent to fully evaporate, while simultaneously increasing the crystallinity of the nanocrystals and resulting in more stable material properties.

[0056] After annealing, the sample was cooled to room temperature to obtain a transparent polymer composite sheet with uniformly dispersed two-dimensional pure iodine perovskite nanocrystals. This sheet, with a thickness of 100-1000 μm, exhibits good optical transparency (visible light transmittance greater than 80%) and mechanical properties. This composite sheet was used as the core waveguide layer of a fluorescent concentrator. Silicon photovoltaic cells, cadmium telluride photovoltaic cells, copper indium gallium selenide photovoltaic cells, or perovskite photovoltaic cells were coupled to its edges using optical coupling agents (such as refractive index matching adhesives) to assemble a complete fluorescent concentrator device. During device operation, the two-dimensional pure iodine perovskite nanocrystals in the composite sheet absorb sunlight and convert it into fluorescence of a specific wavelength. The fluorescence is transmitted to the photovoltaic cells at the edges through total internal reflection within the polymer matrix, achieving light collection and conversion, thereby improving the power generation efficiency of the photovoltaic cells.

[0057] Example 1

[0058] Fabrication of composite materials for flexible fluorescent concentrators adapted to silicon photovoltaic cells

[0059] This embodiment addresses the need for flexible silicon photovoltaic cell modules by selecting polymethyl methacrylate (PMMA), which boasts excellent mechanical properties, as the polymer matrix to prepare a flexible and transparent two-dimensional pure iodine perovskite nanocrystalline composite material thin sheet. The specific steps are as follows:

[0060] Precursor-polymer matrix preparation: Cesium iodide, lead iodide, and n-octylammonium iodide were weighed in a stoichiometric ratio of 1:1:1 and added together to N,N-dimethylformamide solvent. The mixture was magnetically stirred at 500 r / min for 3 h at room temperature until the raw materials were completely dissolved, forming a clear and transparent perovskite precursor solution. Then, PMMA particles were added at a mass fraction of 10%, and stirring was continued for 4 h to completely dissolve the PMMA, resulting in a uniform and precipitate-free mixed slurry. The mixed slurry was then coated onto a flexible polyimide substrate using a spin coating method. The spin coating speed was set to 3000 r / min, and the spin coating time was 60 s, forming a wet film of uniform thickness.

[0061] Liquid-phase thermal injection-induced nucleation: The polyimide substrate carrying the wet film is rapidly transferred to a heating platform protected by an inert atmosphere (nitrogen), and the temperature is rapidly increased to 120°C at a rate of 30°C / min and held at this temperature for 15 min. During this process, the DMF solvent evaporates rapidly, the precursor reaches a supersaturated state in the PMMA network, and the initial nanocrystal nuclei are gradually formed with uniform dispersion, and the flexible framework of PMMA does not deform.

[0062] Vapor-assisted crystallization and dimensional control: Take a sealed glass jar and add a mixture of toluene and methylamine (volume ratio 10:1) to the bottom of the jar. Suspend and fix the nucleated sample in the glass jar (ensure that the sample does not come into contact with the liquid at the bottom of the jar). Place the glass jar in a constant temperature oven at 60°C and keep it at that temperature for 3 hours. Methylamine vapor slowly permeates into the PMMA matrix and coordinates with the lead-iodine octahedra in the initial nanocrystal nuclei, guiding the crystals to grow along the two-dimensional direction and improving the crystallinity.

[0063] Post-processing and device assembly: The sample was removed from the glass jar and annealed in an 80°C oven for 1 hour to remove residual toluene and methylamine. After cooling to room temperature, a flexible composite material sheet attached to a polyimide substrate was obtained. After peeling off the substrate, an independent flexible sheet was obtained. The sheet was used as the core waveguide layer, and flexible silicon photovoltaic cells were coupled around its edges with refractive index matching adhesive. After encapsulation, a flexible fluorescent concentrator device was obtained, which can be adapted to curved surface installation scenarios.

[0064] Example 2

[0065] Preparation of composite materials for high crystallinity fluorescent concentrators

[0066] This embodiment focuses on improving the crystallinity of nanocrystals. By adjusting the parameters of gas-assisted crystallization, a composite material with high fluorescence quantum yield is prepared, suitable for cadmium telluride photovoltaic cells with high light conversion efficiency requirements. The specific steps are as follows:

[0067] Precursor-polymer matrix preparation: Cesium carbonate, lead nitrate, and dodecylammonium iodide were weighed in a stoichiometric ratio of 1:1.1:0.9 and added to dimethyl sulfoxide solvent. The mixture was stirred at 600 r / min for 2.5 h in a 40 °C water bath to form a stable precursor solution. Polystyrene particles were added at a mass fraction of 15% and the mixture was stirred for another 3.5 h to obtain a transparent mixed slurry. The mixed slurry was coated onto a glass substrate using a blade coating method. The wet film thickness was controlled by adjusting the blade gap, and the final wet film thickness was approximately 200 μm.

[0068] Liquid-phase thermal injection-induced nucleation: The glass substrate carrying the wet film was transferred to an argon-protected heating platform and heated to 100°C at a rate of 20°C / min, and held for 20 min; the DMSO solvent slowly evaporated, and the precursor slowly aggregated in the PS network to form uniform initial nanocrystal nuclei. The rigid structure of PS provided stable support for the growth of the crystal nuclei.

[0069] Vapor-phase assisted crystallization and dimensional control: A polytetrafluoroethylene (PTFE) sealed reactor was used. A mixture of xylene and ethylamine (volume ratio 15:1) was added to the bottom of the reactor, and the sample was suspended in the reactor. The reactor was then placed in a constant temperature water bath at 70°C and kept at that temperature for 4 hours. Ethylamine vapor has higher coordination activity than methylamine and can combine with lead-iodine octahedrons more efficiently, promoting directional crystal growth. At the same time, extending the holding time further reduces crystal defects and improves crystallinity.

[0070] Post-processing and device assembly: The sample was removed from the reactor and annealed in a 100°C oven for 1.5 hours to completely remove residual solvent; after cooling, a rigid composite material sheet was obtained attached to the glass substrate (no need to peel off the substrate, the glass is used as the support directly); the sheet was used as a waveguide layer, and cadmium telluride photovoltaic cells were coupled to its long edge. The sheet was then encapsulated with a metal frame to obtain a highly stable rigid fluorescent concentrator device, which can be used in the centralized power generation system of rooftop photovoltaic power stations.

[0071] Example 3

[0072] Preparation of composite materials for low-cost, large-scale production

[0073] This embodiment aims to reduce production costs and adapt to large-scale production. It selects inexpensive and readily available raw materials and simplifies process parameters to prepare low-cost composite materials suitable for low-cost perovskite photovoltaic cell modules. The specific steps are as follows:

[0074] Precursor-polymer matrix preparation: Cesium chloride, lead chloride, and n-butylammonium iodide were weighed in a stoichiometric ratio of 1:1.2:0.8 and added to N-methylpyrrolidone solvent. The mixture was stirred at 400 r / min for 2 h at room temperature to form a precursor solution (chloride raw materials are cheaper than iodides and have good solubility in NMP). Polyvinyl chloride (PVC) particles were added at a mass fraction of 8% and stirred for 3 h until completely dissolved to obtain a mixed slurry. The mixed slurry was poured into a rectangular plastic mold with dimensions of 30 cm × 20 cm by casting and allowed to stand naturally for 1 h to form a uniform wet preform.

[0075] Liquid-phase thermal injection induced nucleation: The mold containing the wet preform is transferred to a nitrogen-protected heating platform and rapidly heated to 110°C at a rate of 40°C / min, and held for 10 min; rapid heating can shorten the solvent evaporation time and improve production efficiency. After the NMP solvent evaporates rapidly, the precursor forms the initial nanocrystal nuclei in the PVC network.

[0076] Vapor-phase assisted crystallization and dimensional control: Take an ordinary sealed plastic container and add a mixture of chlorobenzene and propylamine (volume ratio 20:1, chlorobenzene is cheaper than toluene and xylene and has moderate volatility) to the bottom of the container; suspend the mold and the preform together in the plastic container to avoid contact between the mold and the liquid; place the plastic container in a constant temperature chamber at 50°C and keep it at that temperature for 2 hours (shorten the holding time to improve production efficiency); propylamine vapor permeates into the PVC matrix to achieve two-dimensional growth of nanocrystals and improve crystallinity, meeting the basic performance requirements.

[0077] Post-processing and device assembly: The mold is removed from the plastic can and annealed in a 70°C oven for 2 hours to remove residual solvent; after cooling, the composite material sheet is removed from the mold. The cost of this sheet is significantly lower than that of Examples 1 and 2. It is used as a waveguide layer to couple low-cost perovskite photovoltaic cells at the edge. Through a simple encapsulation process, a low-cost fluorescent concentrator device is obtained, which can be used in cost-sensitive scenarios such as portable solar charging devices.

[0078] The examples provided in this invention are not intended to limit the implementation. Those skilled in the art will recognize that various variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations, and any obvious variations or modifications derived therefrom are still within the scope of this invention.

Claims

1. An in-situ method for the preparation of two-dimensional pure-iodide perovskite nanocrystals for application in fluorescent concentrators, characterized by, The method comprises the following steps: Step 1, precursor-polymer matrix preparation: Dissolve cesium source, lead source and organic long-chain ammonium salt in a strong polar aprotic solvent according to stoichiometric ratio to form a perovskite precursor solution; dissolve a transparent polymer matrix in the perovskite precursor solution, and fully stir to obtain a uniform and transparent mixed slurry; the mixed slurry is prepared into a wet film or a preform with a specific shape by spin coating, blade coating or casting; Step 2, liquid phase hot injection induced nucleation: Transfer the wet film or preform loaded with the precursor obtained in step 1 to a heating platform, and perform rapid heating treatment under the protection of an inert atmosphere; heat to a specific temperature and keep for a short time, so that the solvent is rapidly volatilized, the precursor reaches a supersaturated state in the polymer network and rapidly nucleates to form initial nanocrystal nuclei; Step 3, gas phase assisted crystallization and dimension control: Prepare a gas phase environment containing organic amine vapor, mix a weak polar poor solvent with an appropriate amount of organic amine and place it at the bottom of a sealed container; suspend the sample treated in step 2 in the sealed container without contacting the liquid; heat the entire sealed container at a lower temperature for a period of time, so that the organic amine vapor diffuses and penetrates into the polymer matrix, coordinates with the lead iodine octahedron in the initial nanocrystal nuclei, promotes the directional growth of the two-dimensional layered structure and the perfection of crystallinity, and at the same time controls the thickness of the nanosheet; Step 4, post-treatment and device assembly: Take out the sample treated in step 3 from the gas phase environment, perform annealing treatment to remove residual solvent; after cooling to room temperature, a transparent polymer composite thin plate uniformly dispersed with two-dimensional pure iodine perovskite nanocrystals is obtained; the composite thin plate is used as a core waveguide layer, and a silicon photovoltaic cell or other type of photovoltaic cell is coupled at the edge thereof to assemble a fluorescent concentrator device.

2. The in-situ method for the preparation of two-dimensional pure-iodide perovskite nanocrystals for application in fluorescent concentrators according to claim 1, characterized in that, In step 1, the cesium source is at least one of cesium carbonate, cesium nitrate, cesium chloride or cesium iodide; the lead source is at least one of lead iodide, lead nitrate, lead acetate or lead chloride; the organic long-chain ammonium salt is at least one of n-butylammonium iodide, n-octylammonium iodide, dodecylammonium iodide or hexadecylammonium iodide; the stoichiometric ratio of cesium source, lead source and organic long-chain ammonium salt is 1:(1-1.2):(0.8-1.2).

3. The in-situ method for the synthesis of two-dimensional pure-iodide perovskite nanocrystals for application in fluorescent concentrators according to claim 1, characterized in that, In step 1, the strong polar aprotic solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, N-methyl pyrrolidone or hexamethylphosphoramide; the transparent polymer matrix is at least one of polymethyl methacrylate, polystyrene, polycarbonate or polyvinyl chloride; the mass fraction of the polymer matrix in the mixed slurry is 5%-20%.

4. The in-situ method for the preparation of two-dimensional pure-iodide perovskite nanocrystals for application in fluorescent concentrators according to claim 1, characterized in that, In step 1, the rotation speed of spin coating is 1000-5000 r / min, and the spin coating time is 30-180 s; the wet film thickness of blade coating is 50-500 μm; the shape of the preform of casting is set according to the requirements of the fluorescent concentrator device, including rectangle, circle or trapezoid.

5. The in-situ method for the synthesis of two-dimensional pure-iodide perovskite nanocrystals for application in fluorescent concentrators according to claim 1, characterized in that, In step 2, the inert atmosphere is nitrogen or argon; the rate of rapid heating is 10-50 ℃ / min; the specific temperature is 80-150 ℃, and the holding time is 5-30 min.

6. The in-situ method for the synthesis of two-dimensional pure-iodide perovskite nanocrystals for application in fluorescent concentrators according to claim 1, characterized in that, In the step 3, the weak polar poor solvent is at least one of toluene, benzene, xylene or chlorobenzene; the organic amine is at least one of methylamine, ethylamine, propylamine or butylamine; the volume ratio of the organic amine to the weak polar poor solvent is 1:(5-20).

7. The in-situ method for the synthesis of two-dimensional pure-iodide perovskite nanocrystals for application in fluorescent concentrators according to claim 1, characterized in that, In the step 3, the lower temperature is 40-80℃, and the heating time is 1-6h.

8. The in-situ method for the synthesis of two-dimensional pure-iodide perovskite nanocrystals for application in fluorescent concentrators according to claim 1, characterized in that, In the step 4, the temperature of the annealing treatment is 60-120℃, the annealing time is 0.5-3h, and the thickness of the composite sheet is 100-1000μm.

9. The in-situ method for the synthesis of two-dimensional pure-iodide perovskite nanocrystals for application in fluorescent concentrators according to claim 1, characterized in that, In the step 4, the other type of photovoltaic cell is a cadmium telluride photovoltaic cell, a copper indium gallium selenide photovoltaic cell or a perovskite photovoltaic cell.