Textured structure suitable for perovskite crystalline silicon laminated cell and preparation method thereof

Abstract

The invention relates to the technical field of solar cell manufacturing, provides a pyramid suede structure suitable for a perovskite crystalline silicon laminated cell and a preparation method of the pyramid suede structure, and solves the problems that an existing suede structure is low in light capture efficiency and poor in surface morphology consistency. The method comprises the following steps: selecting a (100) crystal orientation monocrystalline silicon wafer for cleaning treatment; preparing a down solution from a plurality of components including boron-containing ammonium hydroxide, sodium hydroxide, sodium silicate, isopropanol, polyethylene glycol, sodium citrate and the like; uniform nucleation points are formed through chemical pre-etching and beta-cyclodextrin surface modification; wherein the boron-containing ammonium hydroxide is prepared by reacting boric acid with ammonia gas under an alkaline condition. The prepared pyramid suede structure is composed of tetrahedral pyramid units which are regularly arranged. The method is stable in process and good in reproducibility, and the prepared textured structure has excellent light capture efficiency and surface consistency and is suitable for manufacturing efficient perovskite crystalline silicon laminated cells.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cell manufacturing, in particular to a textured structure suitable for perovskite-silicon tandem cell and a preparation method thereof. BACKGROUND

[0002] With the increasing demand for clean energy worldwide, perovskite-silicon tandem solar cells, as the next generation of high-efficiency photovoltaic technology, have become a key path to achieve breakthroughs in solar power generation efficiency. In the structure of peroviskite-silicon tandem solar cells, the surface morphology design of the silicon substrate directly affects the photonic management efficiency and overall device performance. Pyramid textured structure has attracted much attention due to its excellent optical properties. High-efficiency peroviskite-silicon tandem solar cells have extremely strict requirements for the light trapping performance of the silicon substrate surface, which requires the textured structure to have high light trapping efficiency to maximize the utilization of photons, and the surface morphology uniformity to ensure the uniform deposition of peroviskite thin film and the interface quality. Excellent light trapping efficiency can significantly reduce optical loss and improve the short-circuit current density and fill factor of the cell, while the high uniformity of the surface morphology is a prerequisite for forming an ideal heterojunction interface between the peroviskite layer and the silicon substrate, which is directly related to the effective separation and transport of carriers. The realization of these performance requirements is of decisive significance for pushing the efficiency of peroviskite-silicon tandem solar cells to the theoretical limit, and is also the core technical basis for the commercial application and large-scale industrialization of this technology. Therefore, it is of great scientific value and engineering significance to develop a pyramid textured structure preparation technology with optimized optical performance and surface morphology control capability.

[0003] Although the pyramid texture has been widely used in silicon-based solar cells, the existing preparation technology still has significant deficiencies in meeting the special performance requirements of perovskite-silicon tandem cells. Although the traditional alkaline texturing process can form a pyramid structure, due to the randomness of the nucleation mechanism and the non-uniformity of the reaction kinetics during etching, the prepared textured surface structure performs poorly in light capture efficiency, and the surface morphology consistency is poor. For example, CN101414641A discloses a solar cell textured surface and a manufacturing method, but has the problems of low light capture efficiency and poor surface morphology consistency. The root cause of these technical defects is that the existing preparation of textured solution system lacks effective nucleation regulation mechanism, which cannot realize accurate control of the nucleation density and growth orientation of the pyramid, and lacks surface modification technology to optimize the uniformity of the etching process. In addition, the extensive control of reaction conditions in the traditional texturing process leads to a wide distribution of pyramid size, and the morphology parameters are difficult to accurately adjust, which further affects the optimization of optical performance and the quality of perovskite film. The existing technology also generally has the problems of poor process reproducibility and insufficient batch consistency, which is mainly due to insufficient understanding of the etching mechanism and insufficient optimization of process parameters, which seriously restricts the large-scale manufacturing and commercial application of high-performance perovskite-silicon tandem cells. SUMMARY

[0004] (1) Technical problems solved The purpose of the present application is to provide an optimized pyramid textured surface suitable for perovskite-silicon tandem cells, to solve the problems of low light capture efficiency and poor surface morphology consistency of the current textured surface.

[0005] (2) Technical solutions In order to achieve the above purpose, the present application provides the following technical solutions: A preparation method of a textured surface suitable for perovskite-silicon tandem cells, comprising the following steps: S1: selecting a single crystal silicon wafer as a starting material, and cleaning the surface of the silicon wafer; S2: preparing a textured solution, comprising ammonium borohydride, sodium hydroxide, sodium silicate, isopropyl alcohol, polyethylene glycol and sodium citrate; S3: pretreating the silicon wafer to form uniformly distributed nucleation points by chemical pre-etching and β-cyclodextrin surface modification; S4: performing wet pyramid etching to control the etching parameters to obtain pyramid structures of a specified size; S5: subsequent cleaning and drying treatment.

[0006] The ammonium borohydride is prepared by reacting boric acid with ammonia gas under alkaline conditions to form an ammonium tetrahydroxyborate complex, which is concentrated and stored at low temperature.

[0007] Further, the preparation of the velvet solution comprises the following raw materials by weight: 0.1-0.3 parts of ammonium borohydride, 100 parts of deionized water, 1.2-1.8 parts of sodium hydroxide, 1.0-1.5 parts of sodium silicate, 6-8 parts of isopropyl alcohol, 0.05-0.15 parts of polyethylene glycol PEG-4000, 0.02-0.08 parts of sodium citrate, 0.03-0.08 parts of β-cyclodextrin, 0.01-0.03 parts of surfactant sodium dodecyl sulfate, and 0.02-0.05 parts of complex stabilizer disodium ethylenediaminetetraacetate.

[0008] Further, the preparation method of the ammonium borohydride comprises the following steps: adding 100.0 parts of deionized water into a three-necked flask equipped with a stirrer, a thermometer, and a gas inlet tube, adjusting the pH value of the solution to 10.0-11.0 by passing ammonia gas under normal pressure, then adding 3.1-3.7 parts of boric acid under the condition of a stirring rate of 200.0-300.0 rpm, keeping the solution temperature at 25.0-30.0°C during the adding process, then heating the reaction system to a reaction temperature of 40.0-50.0°C at a heating rate of 2.0-3.0°C / min, continuously stirring the reaction at this temperature for 4.0-6.0 h to form a stable ammonium tetrahydroxyborate complex, detecting the pH value every 1.0 h during the reaction process and keeping the pH value stable in the range of 10.0-11.0 by supplementing ammonia gas, then concentrating the reaction mixture under reduced pressure to 30.0-50.0% of the original volume, finally transferring the concentrated solution to a sealed container and storing it at a temperature of 2.0-6.0°C for standby use.

[0009] The present application aims to provide an optimized pyramid texture structure suitable for perovskite crystalline silicon tandem cells and a preparation method thereof, to solve the technical problems of low light capture efficiency, poor surface morphology consistency, uneven pyramid nucleation density, insufficient etching selectivity, poor interface matching with perovskite film, and poor reproducibility in large-area preparation of the current texture structure. By adopting the innovative technical route of multi-component collaborative texturing solution containing ammonium borohydride combined with beta-cyclodextrin surface modification pretreatment, precise regulation of the pyramid nucleation and growth process is achieved. The ammonium borohydride as a mild etchant provides stable and controllable etching activity, the synergistic effect of sodium hydroxide and sodium silicate creates a suitable chemical etching environment, isopropyl alcohol and polyethylene glycol PEG-400 improve the surface tension and wetting properties of the solution, sodium citrate and disodium ethylenediaminetetraacetate act as complexing stabilizers to ensure the chemical stability of the system, and sodium dodecyl sulfate optimizes the interfacial properties. Beta-cyclodextrin forms a uniform distribution of nucleation centers on the silicon surface through a molecular self-assembly mechanism, serving as a nucleating agent to provide a spatial template for the regular growth of pyramids. This multi-component collaborative design achieves comprehensive optimization and control of the pyramid texture structure's nucleation density, growth orientation, size distribution, and surface morphology. Ultimately, a pyramid texture structure with high light capture efficiency, excellent surface uniformity, controllable geometric parameters, and good interface matching is obtained, significantly improving the photoelectric conversion efficiency and device performance stability of perovskite crystalline silicon tandem cells.

[0010] Further, the silicon wafer cleaning process of step S1 includes: selecting a single crystal silicon wafer with a (100) crystal orientation as the substrate material, the silicon wafer thickness is 150-200 μm, the silicon wafer is sequentially placed in acetone, isopropyl alcohol and deionized water for ultrasonic cleaning, each cleaning time is 5-10 minutes, then the silicon wafer is immersed in a mixed solution with a volume ratio of H2SO4:H2O2=3:1, treated at a temperature of 80-90℃ for 10-15 minutes to remove organic contaminants, then the silicon wafer is treated with a 1-2% mass fraction hydrofluoric acid solution for 30-60 seconds to remove the surface oxide layer, finally the silicon wafer surface is rinsed with a large amount of deionized water and dried with nitrogen to obtain a clean silicon wafer.

[0011] Further, the preparation of the texturing solution in step S2 includes: adding deionized water in a reaction vessel equipped with a stirrer and a temperature control system, heating the solution to 75-85°C at a stirring rate of 100-200 rpm, then adding sodium hydroxide in sequence and stirring at a rate of 200-300 rpm for 10-15 min until completely dissolved, then adding sodium silicate and continuing to stir for 10-15 min to ensure uniform mixing, then adding isopropyl alcohol and stirring for 5-8 min, then adding ammonium borohydride, polyethylene glycol PEG-400, sodium citrate, β-cyclodextrin, sodium dodecyl sulfate and disodium ethylenediaminetetraacetate in sequence, stirring for 2-5 min after each component to ensure complete dispersion, finally incubating the mixed solution at a temperature of 75-85°C for 15-30 min to fully complex the components and balance, standing for 2-5 min to stabilize the solution temperature and composition, and finally obtaining a uniform texturing solution.

[0012] Further, the pretreatment in step S3 includes: first placing the cleaned silicon wafer in a dilute sodium hydroxide solution with a mass fraction of 0.1-0.3% for chemical pre-etching treatment, the pre-etching time is 30-60 s, then immersing the silicon wafer in an aqueous solution containing 0.05-0.2% β-cyclodextrin, and performing surface modification treatment at 25-40°C, the treatment time is 120-180 s, immediately after pretreatment, the silicon wafer surface is rinsed with deionized water to remove unbound β-cyclodextrin.

[0013] Further, the wet pyramid etching in step S4 includes: completely immersing the pretreated silicon wafer in the prepared texturing solution and ensuring that there are no air bubbles attached to the surface of the silicon wafer, the immersion depth is 20-50 mm, the solution temperature is controlled at 75-80°C, the etching time is accurately controlled at 25-35 min, the solution is stirred during etching, the stirring speed is 50-100 rpm, and magnetic stirring is used.

[0014] Further, the subsequent cleaning and drying treatment of the step S5 comprises: completing the subsequent cleaning and drying treatment process, taking out the silicon wafer from the preparation of the texturing solution immediately after etching is completed, the taking-out time is ≤ 30s, rinsing the surface of the silicon wafer with a large amount of deionized water for 3-5 times, each time the rinsing time is not less than 2min, the rinsing water resistivity is ≥ 18MΩ·cm, using a dilute hydrochloric acid solution with a mass fraction of 1-3% to treat the silicon wafer for 30-60s to neutralize the residual alkaline substances, the treatment temperature is 20-30℃, rinsing the surface of the silicon wafer with deionized water again until the pH value is close to neutral, the pH value is controlled in the range of 6.5-7.5, placing the silicon wafer in a vacuum drying box with a temperature of 60-80℃ for drying for 15-30min, the vacuum degree is controlled in the range of 0.1-1Pa, the heating rate is 2-5℃ / min, after drying is completed, cooling to room temperature in a nitrogen protection environment, the cooling rate is 1-3℃ / min, and the nitrogen flow is 2-5L / min.

[0015] The application further discloses a texturing structure suitable for the perovskite crystal silicon laminated battery, which is prepared by the method. The pyramid texturing structure is composed of a large number of tetrahedral pyramid units arranged regularly and uniformly in size, and the bottom angle θp of each pyramid unit is averagely 45°-60°. The pyramid bottom side length is averagely 2μm-6μm. The ratio of the pyramid height to the bottom side length is averagely 0.5-0.9. The distribution density of the pyramid on the silicon substrate is averagely 1×10 6 ~2×10 7 cm 2 .

[0016] The application adopts a multi-step precision process control combined with surface pretreatment design, and is mainly used for enhancing the light trapping performance and surface morphology uniformity of the perovskite crystal silicon laminated battery suede structure. The technical scheme realizes the full-flow precise regulation and control of the preparation process of the pyramid suede structure through systematic process optimization, so that the regular surface morphology with ideal optical performance and geometric characteristics is obtained. The design purpose of the silicon wafer cleaning process is to provide a clean and active uniform silicon surface for the subsequent texturing process. By selecting a single crystal silicon wafer with a specific crystal orientation and adopting a multi-stage cleaning system, the thorough removal of surface contaminants and the consistency of the surface state are ensured. The step-by-step cleaning of acetone and isopropyl alcohol effectively removes organic residues, and the oxidizing cleaning of the H2SO4 and H2O2 mixed solution further eliminates deep organic contaminants. The accurate treatment of the hydrofluoric acid solution removes the surface oxide layer and exposes the active silicon surface. The synergistic effect of this multiple cleaning mechanism provides an ideal starting interface for the subsequent chemical etching. The preparation of the suede solution preparation process embodies the concept of precise chemical engineering design. By controlling the feeding sequence and stirring parameters, the ordered complexation and uniform dispersion of the components are realized. The preferential dissolution of sodium hydroxide establishes a stable alkaline environment, the subsequent addition of sodium silicate adjusts the chemical equilibrium of the solution, the introduction of isopropyl alcohol improves the physical and chemical properties of the solution, and the step-by-step addition and sufficient stirring of various functional additives such as boron-containing ammonium hydroxide, polyethylene glycol PEG-400 and sodium citrate ensure the stability and uniformity of the complex multi-component system. The high-temperature holding and stirring process promotes the sufficient complexation and balance among the components, forming a stable solution system with synergistic etching effect. The pretreatment process is the key link to realize the precise control of the surface morphology. The chemical pre-etching of the dilute sodium hydroxide solution produces micro-roughness on the silicon surface and forms initial reaction active points, providing favorable conditions for the subsequent adsorption and self-assembly of beta-cyclodextrin. The surface modification treatment of beta-cyclodextrin forms a uniform distribution of nucleation templates on the silicon surface through its unique molecular structure. The synergistic effect of this double pretreatment mechanism significantly improves the spatial regularity and size consistency of the subsequent pyramid-shaped nucleus. The wet pyramid etching process realizes the controllable growth of the pyramid structure through precise temperature control, time adjustment and stirring optimization. The mild stirring condition ensures the uniformity of the etching process while avoiding mechanical damage. The precise immersion depth control ensures the uniform stress and mass transfer conditions on the surface of the silicon wafer. The synergistic optimization of these process parameters enables the texturing process to accurately follow the preset geometric parameters, and finally forms a regular pyramid array with a specified base angle, edge length, aspect ratio and distribution density.The design purpose of the subsequent cleaning and drying treatment process is to protect the formed pyramid structure and ensure the cleanliness of the surface, multiple deionized water rinsing effectively removes the residual preparation of the pyramidal solution, the neutralization treatment of the dilute hydrochloric acid solution eliminates the surface alkaline residue, the accurate pH control ensures the neutralization of the surface chemical environment, and the combination process of vacuum drying and nitrogen protection avoids oxidation and pollution in the drying process. The systematic post-processing mechanism ensures the integrity of the pyramid surface structure and the surface quality, and through the precise cooperative control of the whole process, a high-performance pyramidal structure composed of regularly arranged and uniform tetrahedral pyramid units is finally obtained, and the light capture efficiency and surface morphology uniformity are significantly improved.

[0017] (3) Beneficial technical effects 1. The present application significantly improves the light capture efficiency and surface morphology uniformity of the pyramid surface structure through the synergistic design of the ammonium hydroxide containing boron multi-component preparation of the pyramidal solution and the surface modification of beta-cyclodextrin, solves the technical problems of random nucleation and poor morphology consistency in traditional texturing process, and provides key technical support for efficient manufacturing of perovskite crystalline silicon tandem battery. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A side view of the pyramid surface structure prepared in Example 3 of the present application.

[0019] Figure 2 A top view of the pyramid surface structure prepared in Example 3 of the present application.

[0020] Figure 3 A cross-sectional view of the pyramid surface structure prepared in Example 3 of the present application.

[0021] Figure 4 A side view of the pyramid surface structure prepared in Comparative Example 1 of the present application.

[0022] Figure 5 A side view of the pyramid surface structure prepared in Comparative Example 3 of the present application.

[0023] Figure 6 A side view of the pyramid surface structure prepared in Comparative Example 6 of the present application.

[0024] Figure 7 A side view of the pyramid surface structure prepared in Comparative Example 9 of the present application.

[0025] Figure 8 A side view of the pyramid surface structure prepared in Comparative Example 12 of the present application. DETAILED DESCRIPTION

[0026] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Embodiments

[0027] A preparation method of a textured structure suitable for a perovskite crystalline silicon stacked cell, comprising the following steps: S1: selecting a single crystal silicon wafer as a starting material, and cleaning the surface of the silicon wafer; including: selecting a single crystal silicon wafer with a crystal direction of (100) as a substrate material, and the thickness of the silicon wafer is 150 μm; sequentially placing the silicon wafer in acetone, isopropyl alcohol and deionized water for ultrasonic cleaning, and the cleaning time is 5 minutes each time; then immersing the silicon wafer in a mixed solution with a volume ratio of H2SO4:H2O2=3:1 at a temperature of 80℃ for 10 minutes to remove organic contaminants; then treating the silicon wafer with a 1% hydrofluoric acid solution for 30 seconds to remove the surface oxide layer; finally, rinsing the surface of the silicon wafer with a large amount of deionized water and blowing dry with nitrogen to obtain a clean silicon wafer.

[0028] S2: preparing a texturing solution, including ammonium borohydride, sodium hydroxide, sodium silicate, isopropyl alcohol, polyethylene glycol and sodium citrate; the preparation of the texturing solution includes: adding deionized water in a reaction container equipped with a stirrer and a temperature control system, heating the solution to 75℃ at a stirring rate of 100 rpm, then adding sodium hydroxide in sequence and stirring at a stirring rate of 200 rpm for 10 min to completely dissolve, then adding sodium silicate and continuing to stir for 10 min to ensure uniform mixing, then adding isopropyl alcohol and stirring for 5 min, then adding ammonium borohydride, polyethylene glycol PEG-400, sodium citrate, β-cyclodextrin, sodium dodecyl sulfate and disodium ethylenediaminetetraacetate in sequence, stirring for 2 min after each component is added to ensure complete dispersion, finally, keeping the mixed solution at a temperature of 75℃ for 15 min to fully complex and balance each component, and standing for 2 min to make the solution temperature and components reach a stable state, and finally obtaining a uniform texturing solution.

[0029] S3: pretreating the silicon wafer to form uniformly distributed nucleation points through chemical pre-etching and β-cyclodextrin surface modification; the pretreatment includes: first, placing the cleaned silicon wafer in a dilute sodium hydroxide solution with a mass fraction of 0.1% for chemical pre-etching treatment, and the pre-etching time is 30 s; then immersing the silicon wafer in an aqueous solution containing β-cyclodextrin with a mass fraction of 0.05%, and performing surface modification treatment at 25℃, and the treatment time is 120 s; after the pretreatment is completed, immediately rinsing the surface of the silicon wafer with deionized water to remove unbound β-cyclodextrin.

[0030] S4: wet pyramid etching is performed, and etching parameters are controlled to obtain pyramid structures with a specified size; the wet pyramid etching comprises: the pretreated silicon wafer is completely immersed in a texturing solution, and it is ensured that no bubbles are attached to the surface of the silicon wafer, the immersion depth is 29 mm, the solution temperature is controlled at 77°C, the etching time is accurately controlled at 28 min, the solution is kept stirring during the etching process, the stirring speed is 65 rpm, and a magnetic stirring mode is adopted.

[0031] S5: subsequent cleaning and drying treatment, which comprises: completing the subsequent cleaning and drying treatment process, taking out the silicon wafer from the texturing solution immediately after the etching is completed, the taking-out time is ≤30 s, rinsing the surface of the silicon wafer with a large amount of deionized water for 4 times, each time for no less than 2 min, the water resistivity is ≥18 MΩ·cm, treating the silicon wafer with a dilute hydrochloric acid solution with a mass fraction of 2% for 39 s to neutralize residual alkaline substances, the treatment temperature is 23°C, rinsing the surface of the silicon wafer with deionized water again until the pH value is close to neutral, the pH value is controlled within the range of 6.8, and placing the silicon wafer in a vacuum drying box with a temperature of 66°C for drying for 20 min, the vacuum degree is controlled at 0.4 Pa, the temperature rising rate is 3°C / min, after the drying is completed, cooling to room temperature under the protection of a nitrogen atmosphere, the cooling rate is 2°C / min, and the nitrogen flow rate is 3 L / min.

[0032] The ammonium hydroxide containing boron is prepared by reacting boric acid with ammonia gas under alkaline conditions to form an ammonium tetrahydroxyborate complex, and then concentrated and stored at low temperature.

[0033] The texturing solution of the embodiment comprises the following raw materials in parts by weight: 0.2 parts of ammonium hydroxide containing boron, 100 parts of deionized water, 1.4 parts of sodium hydroxide, 1.2 parts of sodium silicate, 7 parts of isopropyl alcohol, 0.08 parts of polyethylene glycol PEG-400, 0.04 parts of sodium citrate, 0.05 parts of β-cyclodextrin, 0.02 parts of surfactant sodium dodecyl sulfate, and 0.03 parts of complex stabilizer disodium ethylenediaminetetraacetate. The preparation method of the ammonium hydroxide containing boron of the embodiment is as follows: in a three-necked flask provided with a stirrer, a thermometer and a gas inlet pipe, 100.0 parts of deionized water is added, ammonia gas is introduced under normal pressure to adjust the pH value of the solution to 10.3, then 3.3 parts of boric acid is added under the condition that the stirring rate is 230.0 rpm, the solution temperature is kept at 26.5°C during the adding process, then the reaction system is heated to a reaction temperature of 43.0°C at a heating rate of 2.3°C / min, the stable ammonium tetrahydroxyborate complex is formed by continuously stirring at this temperature for 4.6 h, the pH value is detected every 1.0 h during the reaction process, and the pH value is kept stable within the range of 10.3 by supplementing ammonia gas, then the reaction mixture is concentrated under reduced pressure to 36.0% of the original volume, finally the concentrated solution is transferred to a sealed container for storage at a temperature of 3.2°C for standby use.

[0034] The embodiment is a kind of suitable for perovskite crystalline silicon laminated cell's rough structure, it is prepared by the above method; The pyramid rough structure of the embodiment is composed of a large number of regularly arranged and uniformly sized tetrahedral pyramid units, the base angle θp of each pyramid unit is 50° on average, and the base length of the pyramid is 2 μm on average; The ratio of the height of the pyramid to the base length is 0.5 on average, and the distribution density of the pyramid on the silicon substrate is 2×10 7 Individual / cm 2 . Embodiment

[0035] A preparation method of a rough structure suitable for perovskite crystalline silicon laminated cell, comprising the following steps: S1: Selecting a single crystal silicon wafer as a starting material, cleaning the surface of the silicon wafer; including: selecting a single crystal silicon wafer with a crystal direction of (100) as a substrate material, the thickness of the silicon wafer is 165 μm, the silicon wafer is sequentially placed in acetone, isopropyl alcohol and deionized water for ultrasonic cleaning, each time for 7 minutes, then the silicon wafer is immersed in a mixed solution with a volume ratio of H2SO4:H2O2=3:1, treated at a temperature of 83℃ for 12 minutes to remove organic contaminants, then the silicon wafer is treated with a 1.3% hydrofluoric acid solution for 39 seconds to remove the surface oxide layer, and finally the surface of the silicon wafer is washed with a large amount of deionized water and dried with nitrogen to obtain a clean silicon wafer.

[0036] S2: Preparing a texturing solution containing ammonium borohydride, sodium hydroxide, sodium silicate, isopropyl alcohol, polyethylene glycol and sodium citrate; the preparation of the texturing solution includes: adding deionized water in a reaction vessel equipped with a stirrer and a temperature control system, heating the solution to 78℃ under the condition of stirring rate of 130 rpm, then adding sodium hydroxide in sequence and stirring at a stirring rate of 230 rpm for 12 min to completely dissolve, then adding sodium silicate and continuing to stir for 12 min to ensure uniform mixing, then adding isopropyl alcohol and stirring for 6 min, then adding ammonium borohydride, polyethylene glycol PEG-400, sodium citrate, β-cyclodextrin, sodium dodecyl sulfate and disodium ethylenediaminetetraacetate in sequence, each component is stirred for 3 min to ensure complete dispersion, finally the mixed solution is incubated at a temperature of 78℃ for 20 min to make each component fully complex and balance, and the solution temperature and components are stable after standing for 3 min, finally a uniform texturing solution is obtained.

[0037] S3: Pretreatment of the silicon wafer, forming uniform distribution of nucleation points by chemical pre-etching and β-cyclodextrin surface modification; the pretreatment includes: firstly, placing the cleaned silicon wafer in a dilute sodium hydroxide solution with a mass fraction of 0.2% for chemical pre-etching treatment, the pre-etching time is 39s, then immersing the silicon wafer in an aqueous solution containing 0.10% mass fraction of β-cyclodextrin, and performing surface modification treatment at 30℃, the treatment time is 138s, immediately after the pretreatment, rinsing the surface of the silicon wafer with deionized water to remove unbound β-cyclodextrin.

[0038] S4: Wet pyramid etching, controlling the etching parameters to obtain pyramid structures of specified size; the wet pyramid etching includes: completely immersing the pretreated silicon wafer in the texturing solution and ensuring that there is no bubble attached to the surface of the silicon wafer, the immersion depth is 20mm, the solution temperature is controlled at 75℃, the etching time is accurately controlled at 25min, the solution is stirred during the etching process, the stirring speed is 50rpm, and the magnetic stirring method is adopted.

[0039] S5: Subsequent cleaning and drying treatment, which includes: completing the subsequent cleaning and drying treatment process, immediately after the etching is completed, the silicon wafer is taken out from the texturing solution, the taking-out time is ≤30s, the surface of the silicon wafer is rinsed with a large amount of deionized water for 3 times, each rinsing time is not less than 2min, the resistivity of the rinsing water is ≥18MΩ·cm, the silicon wafer is treated with a dilute hydrochloric acid solution with a mass fraction of 1% for 30s to neutralize the residual alkaline substances, the treatment temperature is 20℃, the surface of the silicon wafer is again rinsed with deionized water until the pH value is close to neutral, the pH value is controlled within the range of 6.5, the silicon wafer is placed in a vacuum drying box with a temperature of 60℃ for drying for 15min, the vacuum degree is controlled at 0.1Pa, the heating rate is 2℃ / min, after the drying is completed, the silicon wafer is cooled to room temperature under the protection of nitrogen atmosphere, the cooling rate is 1℃ / min, and the nitrogen flow rate is 2L / min.

[0040] The ammonium hydroxide containing boron is prepared by reacting boric acid with ammonia gas under alkaline conditions to form an ammonium tetrahydroxyborate complex, and then concentrated and stored at low temperature.

[0041] The texturing solution of the embodiment contains the following raw materials in parts by weight: ammonium hydroxide containing boron 0.1 part, deionized water 100 parts, sodium hydroxide 1.2 parts, sodium silicate 1.0 part, isopropyl alcohol 6 parts, polyethylene glycol PEG-400 0.05 part, sodium citrate 0.02 part, β-cyclodextrin 0.03 part, surfactant sodium dodecyl sulfate 0.01 part, complexing stabilizer disodium ethylenediaminetetraacetate 0.02 part.

[0042] The preparation method of the ammonium borohydride-containing solution of the present embodiment is as follows: 100.0 parts by weight of deionized water is added into a three-necked flask equipped with a stirrer, a thermometer and a gas inlet pipe, and ammonia gas is introduced to adjust the pH value of the solution to 10.0 under normal pressure, then 3.1 parts by weight of boric acid is added under the condition of a stirring rate of 200.0 rpm, the temperature of the solution is kept at 25.0°C during the addition, then the reaction system is heated to a reaction temperature of 40.0°C at a heating rate of 2.0°C / min, the stirring is continued at this temperature for 4.0 h to form a stable ammonium tetra-borate complex, the pH value is detected every 1.0 h during the reaction and ammonia gas is supplemented to keep the pH value stable within the range of 10.0, then the reaction mixture is concentrated to 30.0% of the original volume under reduced pressure, and finally the concentrated solution is transferred to a sealed container and stored at a temperature of 2.0°C for standby use.

[0043] The texturing structure suitable for the perovskite crystalline silicon tandem cell of the present embodiment is prepared by the above method; The pyramid texturing structure of the present embodiment is composed of a large number of tetrahedral pyramid units arranged regularly and uniformly in size, the average base angle θp of each pyramid unit is 50°, the average base length of the pyramid is 2 μm; The average ratio of the height to the base length of the pyramid is 0.6, and the average distribution density of the pyramid on the silicon substrate is 1.1×10 7 cm 2 . Embodiment

[0044] A preparation method of a texturing structure suitable for a perovskite crystalline silicon tandem cell, comprising the following steps: S1: selecting a single crystal silicon wafer as a starting material and performing cleaning treatment on the surface of the silicon wafer; including: selecting a single crystal silicon wafer with a crystal orientation of (100) as a substrate material, the thickness of the silicon wafer is 180 μm, the silicon wafer is sequentially placed in acetone, isopropyl alcohol and deionized water for ultrasonic cleaning, each time for 8 minutes, then the silicon wafer is immersed in a mixed solution with a volume ratio of H2SO4:H2O2=3:1, treated at a temperature of 86°C for 13 minutes to remove organic contaminants, then the silicon wafer is treated with a hydrofluoric acid solution with a mass fraction of 1.6% for 48 seconds to remove the surface oxide layer, and finally the surface of the silicon wafer is rinsed with a large amount of deionized water and dried with nitrogen to obtain a clean silicon wafer.

[0045] S2: Preparation of texturing solution, including ammonium borohydride, sodium hydroxide, sodium silicate, isopropyl alcohol, polyethylene glycol and sodium citrate; the preparation of texturing solution includes: adding deionized water in a reaction vessel equipped with a stirrer and a temperature control system, heating the solution to 81℃ at a stirring rate of 160 rpm, then adding sodium hydroxide in sequence and stirring at a stirring rate of 260 rpm for 13 min to completely dissolve, then adding sodium silicate and continuing to stir for 13 min to ensure uniform mixing, then adding isopropyl alcohol and stirring for 7 min, then adding ammonium borohydride, polyethylene glycol PEG-400, sodium citrate, β-cyclodextrin, sodium dodecyl sulfate and disodium ethylenediaminetetraacetate in sequence, stirring for 4 min after each component to ensure complete dispersion, finally, the mixed solution is incubated at a temperature of 81℃ for 24 min to fully complex the components, and the solution temperature and components are allowed to reach a stable state after standing for 4 min, and a uniform texturing solution is finally obtained.

[0046] S3: Pretreatment of silicon wafer, forming uniformly distributed nucleation points by chemical pre-etching and β-cyclodextrin surface modification; the pretreatment includes: first, the cleaned silicon wafer is placed in a dilute sodium hydroxide solution with a mass fraction of 0.2% for chemical pre-etching treatment, the pre-etching time is 48 s, then the silicon wafer is immersed in an aqueous solution containing 0.14% β-cyclodextrin by mass fraction, and surface modification treatment is carried out at 34℃, the treatment time is 156 s, and the silicon wafer surface is rinsed with deionized water immediately after pretreatment to remove unbound β-cyclodextrin.

[0047] S4: Wet pyramid etching, control the etching parameters to obtain pyramid structure with specified size; wet pyramid etching includes: the pretreated silicon wafer is completely immersed in the texturing solution and the silicon wafer surface is ensured to have no bubble attachment, the immersion depth is 50 mm, the solution temperature is controlled at 80℃, the etching time is accurately controlled at 35 min, the solution is stirred during etching, the stirring speed is 100 rpm, and magnetic stirring method is adopted.

[0048] S5: subsequent cleaning and drying treatment, the subsequent cleaning and drying treatment comprising: completing the subsequent cleaning and drying treatment process, taking out the silicon wafer from the texturing solution immediately after etching is completed, the taking-out time being ≤30 s, rinsing the surface of the silicon wafer with a large amount of deionized water 5 times, each time for no less than 2 min, the resistivity of the rinsing water being ≥18 MΩ·cm, treating the silicon wafer with a dilute hydrochloric acid solution with a mass fraction of 3% for 60 s to neutralize residual alkaline substances, the treatment temperature being 30°C, rinsing the surface of the silicon wafer again with deionized water until the pH value is close to neutral, the pH value being controlled within the range of 7.5, and drying the silicon wafer in a vacuum drying box at a temperature of 80°C for 30 min, the vacuum degree being controlled at 1 Pa, the temperature rising rate being 5°C / min, cooling the silicon wafer to room temperature under a nitrogen protection environment after drying is completed, the cooling rate being 3°C / min, and the nitrogen flow being 5 L / min.

[0049] The ammonium hydroxide containing boron is prepared by reacting boric acid with ammonia gas under alkaline conditions to form an ammonium tetrahydroxyborate complex, and then concentrated and stored at low temperature.

[0050] The texturing solution of this embodiment comprises the following raw materials in parts by weight: ammonium hydroxide containing boron 0.3 parts, deionized water 100 parts, sodium hydroxide 1.8 parts, sodium silicate 1.5 parts, isopropyl alcohol 8 parts, polyethylene glycol PEG-400 0.15 parts, sodium citrate 0.08 parts, β-cyclodextrin 0.08 parts, surfactant sodium dodecyl sulfate 0.03 parts, and complex stabilizer disodium ethylenediaminetetraacetate 0.05 parts.

[0051] The preparation method of the ammonium hydroxide containing boron of this embodiment is as follows: in a three-necked flask equipped with a stirrer, a thermometer and a gas inlet pipe, 100.0 parts of deionized water is added, ammonia gas is introduced under normal pressure to adjust the pH value of the solution to 11.0, then 3.7 parts of boric acid is added under the condition that the stirring rate is 300.0 rpm, the solution temperature is kept at 30.0°C during the adding process, then the reaction system is heated to a reaction temperature of 50.0°C at a heating rate of 3.0°C / min, the stable ammonium tetrahydroxyborate complex is formed by continuously stirring at this temperature for 6.0 h, the pH value is detected every 1.0 h during the reaction process, and the pH value is kept stable within the range of 11.0 by supplementing ammonia gas, then the reaction mixture is concentrated to 50.0% of the original volume under reduced pressure, and finally the concentrated solution is transferred to a sealed container for storage at a temperature of 6.0°C for standby use.

[0052] The texturing structure of this embodiment is suitable for a perovskite crystalline silicon stacked cell and is prepared by the above method. The pyramid suede structure of the embodiment is composed of a large number of tetrahedral pyramid units arranged regularly and uniformly in size, the bottom angle θp of each pyramid unit is 55° on average, the length of the bottom of the pyramid is 5 μm on average, the ratio of the height of the pyramid to the length of the bottom is 0.8 on average, and the distribution density of the pyramid on the silicon substrate is 4×10 6 cm 2 . Embodiment

[0053] A preparation method of a suede structure suitable for a perovskite crystalline silicon laminated cell, comprising the following steps: S1: selecting a single crystal silicon wafer as a starting material, and performing cleaning treatment on the surface of the silicon wafer; including: selecting a single crystal silicon wafer with a crystal direction of (100) as a substrate material, the thickness of the silicon wafer is 200 μm, and the silicon wafer is sequentially placed in acetone, isopropyl alcohol and deionized water for ultrasonic cleaning, each time for 10 minutes, then the silicon wafer is immersed in a mixed solution with a volume ratio of H2SO4:H2O2=3:1, treated at a temperature of 90℃ for 15 minutes to remove organic contaminants, then the silicon wafer is treated with a 2% hydrofluoric acid solution for 60 seconds to remove the surface oxide layer, and finally the surface of the silicon wafer is rinsed with a large amount of deionized water and dried with nitrogen to obtain a clean silicon wafer.

[0054] S2: preparing a suede solution containing ammonium borohydride, sodium hydroxide, sodium silicate, isopropyl alcohol, polyethylene glycol and sodium citrate; the preparation of the suede solution includes: adding deionized water in a reaction container equipped with a stirrer and a temperature control system, heating the solution to 85℃ under the condition of a stirring rate of 200 rpm, then adding sodium hydroxide in sequence and stirring at a stirring rate of 300 rpm for 15 min to completely dissolve, then adding sodium silicate and continuing to stir for 15 min to ensure uniform mixing, then adding isopropyl alcohol and stirring for 8 min, then adding ammonium borohydride, polyethylene glycol PEG-400, sodium citrate, β-cyclodextrin, sodium dodecyl sulfate and disodium ethylenediaminetetraacetate in sequence, each component is stirred for 5 min after adding to ensure complete dispersion, finally the mixed solution is incubated at a temperature of 85℃ for 30 min to fully complex and balance each component, and the solution temperature and components are stable after standing for 5 min, and finally a uniform suede solution is obtained.

[0055] S3: Pretreatment of the silicon wafer, forming uniform distribution of nucleation points by chemical pre-etching and β-cyclodextrin surface modification; the pretreatment includes: firstly, placing the cleaned silicon wafer in a dilute sodium hydroxide solution with a mass fraction of 0.3% for chemical pre-etching treatment, the pre-etching time is 60s, then immersing the silicon wafer in an aqueous solution containing 0.2% mass fraction of β-cyclodextrin, and performing surface modification treatment at 40℃, the treatment time is 180s, immediately after the pretreatment, rinsing the surface of the silicon wafer with deionized water to remove unbound β-cyclodextrin.

[0056] S4: Wet pyramid etching, controlling the etching parameters to obtain pyramid structures of specified size; the wet pyramid etching includes: completely immersing the pretreated silicon wafer in the texturing solution and ensuring that there is no bubble attached to the surface of the silicon wafer, the immersion depth is 38mm, the solution temperature is controlled at 78℃, the etching time is accurately controlled at 31min, the solution is stirred during the etching process, the stirring speed is 80rpm, and the magnetic stirring method is adopted.

[0057] S5: Subsequent cleaning and drying treatment, which includes: completing the subsequent cleaning and drying treatment process, immediately after the etching is completed, the silicon wafer is taken out from the texturing solution, the taking-out time is ≤30s, the surface of the silicon wafer is rinsed with a large amount of deionized water for 4 times, each rinsing time is not less than 2min, the resistivity of the rinsing water is ≥18MΩ·cm, the silicon wafer is treated with a dilute hydrochloric acid solution with a mass fraction of 2% for 48s to neutralize the residual alkaline substances, the treatment temperature is 26℃, the surface of the silicon wafer is again rinsed with deionized water until the pH value is close to neutral, the pH value is controlled within the range of 7.1, the silicon wafer is placed in a vacuum drying box with a temperature of 72℃ for drying for 24min, the vacuum degree is controlled at 0.6Pa, the heating rate is 4℃ / min, after the drying is completed, the silicon wafer is cooled to room temperature under the protection of nitrogen atmosphere, the cooling rate is 2℃ / min, and the nitrogen flow rate is 4L / min.

[0058] The ammonium hydroxide containing boron is prepared by reacting boric acid with ammonia gas under alkaline conditions to form an ammonium tetrahydroxyborate complex, which is concentrated and stored at low temperature.

[0059] The texturing solution of the embodiment contains the following raw materials in parts by weight: ammonium hydroxide containing boron 0.2 parts, deionized water 100 parts, sodium hydroxide 1.6 parts, sodium silicate 1.3 parts, isopropyl alcohol 7 parts, polyethylene glycol PEG-400 0.11 parts, sodium citrate 0.06 parts, β-cyclodextrin 0.06 parts, surfactant sodium dodecyl sulfate 0.02 parts, complexing stabilizer disodium ethylenediaminetetraacetate 0.04 parts.

[0060] The preparation method of the ammonium borohydride-containing solution of the present embodiment is as follows: 100.0 parts of deionized water is added into a three-necked flask equipped with a stirrer, a thermometer and a gas inlet tube, and ammonia gas is introduced to adjust the pH value of the solution to 10.6 under normal pressure, then 3.5 parts of boric acid is added under the condition of a stirring rate of 260.0 rpm, and the temperature of the solution is kept at 28.0°C during the addition process, then the reaction system is heated to a reaction temperature of 46.0°C at a heating rate of 2.6°C / min, and the stirring is continued at this temperature for 5.2 h to form a stable ammonium tetra-borate complex, the pH value is detected every 1.0 h during the reaction process, and the pH value is kept stable in the range of 10.6 by supplementing ammonia gas, then the reaction mixture is concentrated to 42.0% of the original volume under reduced pressure, and finally the concentrated solution is transferred to a sealed container and stored at a temperature of 4.4°C for standby use.

[0061] The texturing structure suitable for the perovskite crystalline silicon tandem cell of the present embodiment is prepared by the above method; The pyramid texturing structure of the present embodiment is composed of a large number of tetrahedral pyramid units arranged in a regular manner and having uniform sizes, the average base angle θp of each pyramid unit is 60°, the average base length of the pyramid is 6 μm, the average ratio of the height to the base length of the pyramid is 0.9, and the average distribution density of the pyramid on the silicon substrate is 1×10 6 cm 2 .

[0062] Comparative Example 1 The same as Example 1, except that no ammonium borohydride-containing solution is added in the texturing solution, and only 1.2 parts of sodium hydroxide is used as the etchant for pyramid texturing.

[0063] Comparative Example 2 The same as Example 1, except that no β-cyclodextrin is added in the texturing solution, and the content of other components remains unchanged.

[0064] Comparative Example 3 The same as Example 1, except that only a 0.1% dilute sodium hydroxide solution is used for chemical pre-etching treatment for 30 seconds in the pretreatment step S3, and no β-cyclodextrin surface modification treatment is performed.

[0065] Comparative Example 4 The same as Example 1, except that the reaction temperature in the preparation process of the ammonium borohydride-containing solution is 60°C, and the reaction time is 2 hours, and other preparation parameters remain unchanged.

[0066] Comparative Example 5 The same as example 1, the difference is that the polyethylene glycol PEG-400 and sodium citrate are not added in the texturing solution, and the content of other components and the preparation process parameters remain unchanged.

[0067] Comparative example 6 The same as example 1, the difference is that the solution temperature is controlled to be 60℃ in the wet pyramid etching process, and the etching time is 50 minutes, and other etching parameters remain unchanged.

[0068] Comparative example 7 The same as example 1, the difference is that the mass fraction of 5% hydrofluoric acid solution is used to treat the silicon wafer for 120 seconds to remove the surface oxide layer in the silicon wafer cleaning process, and other cleaning steps remain unchanged.

[0069] Comparative example 8 The same as example 1, the difference is that the solution temperature is heated to 50℃ during the preparation of the texturing solution, and the temperature of the incubator is 50℃, and other preparation parameters remain unchanged.

[0070] Comparative example 9 The same as example 1, the difference is that the mass fraction of 2% sodium hydroxide solution is used for chemical pre-etching in the pretreatment step for 120 seconds, and the surface modification treatment temperature of β-cyclodextrin is 60℃, and the treatment time is 60 seconds.

[0071] Comparative example 10 The same as example 1, the difference is that the pH value of the solution is adjusted to 8.0 by passing ammonia gas during the preparation of the ammonium hydroxide containing boron, and the pH value is kept stable in the range of 8.0 during the reaction, and other preparation parameters remain unchanged.

[0072] Comparative example 11 The same as example 1, the difference is that the sodium dodecyl sulfate and disodium ethylenediaminetetraacetate are not added in the texturing solution, and the content of other components and the preparation process parameters remain unchanged.

[0073] Comparative example 12 The same as example 1, the difference is that the single crystal silicon wafer with (111) crystal orientation is selected as the substrate material in the silicon wafer cleaning process, and other cleaning steps and parameters remain unchanged.

[0074] Figure 1 The side view of the pyramid texture structure prepared in example 3 of the present application, from which it can be clearly observed that the pyramid units are arranged in order, the size is uniform, and the surface morphology is regular, which proves the superiority and stability of the preparation process of the present application, Figure 2The top view of the pyramid suede structure prepared in Example 3 of the present application can determine the base angle θp as 55° by measuring the included angle between the base edge and the adjacent edge, which meets the ideal pyramid geometric structure requirement, Figure 3 The cross-sectional view of the pyramid suede structure prepared in Example 3 of the present application shows the complete three-dimensional profile and internal structural features of the pyramid, further verifying the accuracy of the preparation process, Figure 4 The side view of the pyramid suede structure prepared in Comparative Example 1 of the present application shows that the etching is not uniform and forms irregular morphology due to the lack of etching ability caused by not adding boron-containing ammonium hydroxide in the suede solution, and the pyramid structure lacks regularity, Figure 5 The side view of the pyramid suede structure prepared in Comparative Example 3 of the present application shows that the nucleation template is missing due to the lack of β-cyclodextrin surface modification treatment in the pretreatment step, and the pyramid nucleation point is observed to be rare, with a distribution density significantly lower than the example, and the overall coverage is insufficient, Figure 6 The side view of the pyramid suede structure prepared in Comparative Example 6 of the present application shows that the solution temperature is too low (60°C) and the etching time is too long (50 minutes) during the wet etching process, resulting in the formation of a shallow pyramid structure, and the measurement result shows that the base angle θp is only 41°, which is far lower than the ideal value, affecting the light trapping effect, Figure 7 The side view of the pyramid suede structure prepared in Comparative Example 9 of the present application shows that the uniformity of the silicon surface is destroyed by excessive pretreatment, as the 2% sodium hydroxide solution is used for 120 seconds and the β-cyclodextrin treatment temperature is as high as 60°C, and the pyramid morphology is irregular and the size difference is large, Figure 8 The side view of the pyramid suede structure prepared in Comparative Example 12 of the present application shows that the anisotropic etching effect is poor due to the mismatch of the crystal direction of the (111) silicon wafer as the substrate material, and the regular pyramid structure cannot be formed, and the surface morphology is obviously observed to be chaotic and disordered, lacking clear geometric features.

[0075] Performance test: To test the performance of the pyramid texture, the preparation process of the perovskite film includes first pre-treating the pyramid textured silicon wafer, placing the silicon wafer in an ultraviolet ozone cleaning machine for 15 minutes to remove organic contaminants, and then performing subsequent preparation in a nitrogen glove box. When preparing the perovskite precursor solution, 159 mg of methylammonium iodide, 172 mg of formamidinium iodide, 461 mg of lead iodide, and 73 mg of lead bromide are dissolved in a mixed solvent of 0.8 mL of dimethylformamide and 0.2 mL of dimethyl sulfoxide. The solution is stirred at 60°C for 2 hours until it is completely dissolved to obtain a 1.4M perovskite precursor solution. When preparing the additive solution, 0.5% by volume of 1,8-diiodooctane is added to chlorobenzene as an additive for standby use. The perovskite film deposition is performed using a two-step spin coating method. The first step is spin coating at 500 rpm for 10 seconds, and the second step is spin coating at 4000 rpm for 30 seconds. At 8 seconds before the end of spin coating, 100 μL of chlorobenzene additive solution is quickly added for anti-solvent treatment. After spin coating, the sample is immediately transferred to a 100°C hot plate for annealing for 10 minutes to crystallize the perovskite. Due to the three-dimensional topography of the pyramid texture, the amount of precursor solution needs to be appropriately increased to 150 μL to ensure complete coverage of the texture. During spin coating, a step-by-step acceleration method is used, i.e., first pre-spinning at 200 rpm for 5 seconds to wet the texture with the solution, and then performing the normal two-step spin coating procedure. The addition time and amount of anti-solvent treatment need to be precisely controlled to avoid impacting the texture. During annealing, the annealing time is extended to 15 minutes, and a gradient heating method is used, i.e., first pre-heating at 80°C for 2 minutes, then heating to 100°C for 13 minutes. The entire preparation process needs to be performed in a nitrogen environment with a humidity of less than 10% to prevent degradation of the perovskite film. After preparation, XRD, SEM, UV-vis, and other characterization tests should be performed immediately to evaluate the crystalline quality, uniformity of coverage, and optical properties of the perovskite film on the texture.

[0076] Reflectance spectrum test experiment: The reflectance characteristics of the pyramid texture were tested using a UV-visible-near infrared spectrophotometer equipped with an integrating sphere accessory. The test object was the reflectance spectrum curve in the wavelength range of 300-1200 nm. The experimental conditions were set as follows: incident angle 8°, scanning speed 240 nm / min, data interval 1 nm, and polytetrafluoroethylene standard white board as 100% reflectance reference. Baseline correction and dark current correction were required before testing. The reflectance values in the visible light region of 400-800 nm and the near-infrared region of 800-1200 nm were focused on, and the weighted average reflectance was calculated to evaluate the light capture performance.

[0077] Optical absorption ability test (UV-Vis): To investigate the light absorption enhancement effect of perovskite films on the surface of the textured structure, the transmittance and absorbance were tested by UV-Vis spectrophotometer (PerkinElmer Lambda 950). The test object was the optical absorption characteristics of perovskite films in the wavelength range of 300-900 nm. The experimental conditions were set as follows: the incident angle was kept vertical, the scanning speed was 240 nm / min, the data interval was 1 nm, and the absorption spectra of perovskite films on the flat silicon wafer and the pyramid textured structure were tested respectively. The light capture efficiency improvement was evaluated by comparing the differences in absorption spectra, and the optical band gap and absorption edge movement were analyzed.

[0078] Photoelectric conversion performance test (J-V): The simple device structure FTO / c-TiO2 / mp-TiO2 / perovskite / HTL / Au was assembled for photoelectric performance test. The test object was the electrical output characteristics of the complete perovskite solar cell device. The experimental conditions were set as follows: standard test conditions (AM1.5G spectrum, light intensity 100 mW / cm 2 , device temperature 25℃), J-V curve was tested by solar simulator and source table instrument (such as Keithley 2400), scanning voltage range-0.2V to 1.2V, scanning speed 50mV / s, forward and reverse scanning were carried out respectively to evaluate the hysteresis effect, and key parameters such as open circuit voltage Voc, short circuit current density Jsc, fill factor FF and photoelectric conversion efficiency PCE were extracted to directly evaluate the enhancement effect of textured structure on photoelectric performance.

[0079] The properties of the experiments of Examples 1-4 and Comparative Examples 1-12 are gathered in Table 1. As can be seen from Table 1, the lack of addition of boron-containing ammonium hydroxide in the texturing solution leads to insufficient etching ability, irregular pyramid morphology, significantly increased reflectivity, decreased light capture efficiency, and significantly reduced final photoelectric conversion efficiency. The lack of β-cyclodextrin surface modifier in the texturing solution or the pretreatment process leads to uneven distribution of nucleation points, poor consistency of pyramid size, increased reflectivity, and slightly decreased photoelectric performance. Improper preparation conditions of the boron-containing ammonium hydroxide, such as excessively high reaction temperature or excessively low pH value, affect the complex stability and etching activity, leading to unsatisfactory texturing effect and slight performance decline. The lack of functional additives such as polyethylene glycol PEG-400 and sodium citrate in the texturing solution affects the wettability and chemical equilibrium of the solution, resulting in poor uniformity of the pyramid morphology and decreased photoelectric efficiency. Excessively low texturing temperature or excessively long time leads to insufficient etching or over-etching, forming irregular surface morphology, significantly increased reflectivity, and significantly decreased photoelectric performance. Excessively high concentration of hydrofluoric acid or excessively long treatment time causes excessive corrosion of the silicon surface, affecting the subsequent film formation quality, but has relatively small effect on the optical performance. Excessively low preparation temperature of the texturing solution affects the dissolution and complexation of the components, leading to poor solution stability, decreased texturing uniformity, and greatly reduced photoelectric efficiency. Excessively strong pretreatment conditions can damage the silicon surface structure, and excessively high pretreatment temperature or improper time affects the adsorption effect of β-cyclodextrin, leading to failure of nucleation control and significant performance decline. The lack of surfactants and complex stabilizers in the texturing solution affects the dispersion stability of the solution and the synergistic effect of the components, but has relatively limited effect on the overall performance due to the small amount of addition. The improper selection of silicon wafer crystal orientation, such as using (111) crystal orientation instead of (100) crystal orientation, significantly affects the anisotropic etching effect, making it difficult to form regular pyramid structures, leading to a significant decrease in light capture performance and a serious reduction in photoelectric conversion efficiency.

[0080] Table 1: Properties of Examples 1-4 and Comparative Examples 1-12

[0081] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and not to limit them. Although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that any equivalent structural transformation made within the concept of the present application, using the contents of the present application specification and drawings, should be covered within the scope of protection of the claims of the present application.

Claims

1. A method for preparing a velvet structure suitable for perovskite silicon tandem cells, characterized in that: The following steps are involved: S1: Select a single crystal silicon wafer as the starting material and clean the surface of the silicon wafer; S2: preparing a velvet solution comprising boron-containing ammonium hydroxide, sodium hydroxide, sodium silicate, isopropyl alcohol, polyethylene glycol, and sodium citrate; S3: Pre-treating the silicon wafer to form uniformly distributed nucleation sites through chemical pre-etching and β-cyclodextrin surface modification; S4: performing wet pyramid etching and controlling etching parameters to obtain a pyramid structure of a specified size; S5: subsequent cleaning and drying; The boron-containing ammonium hydroxide is prepared by reacting boric acid with ammonia gas under alkaline conditions to form an ammonium tetraborate hydroxide complex, which is concentrated and then stored at low temperature.

2. The method for preparing a textured structure suitable for a perovskite silicon tandem cell according to claim 1, wherein: The velvet preparation solution comprises the following raw materials in parts by weight: 0.1-0.3 parts of boron-containing ammonium hydroxide, 100 parts of deionized water, 1.2-1.8 parts of sodium hydroxide, 1.0-1.5 parts of sodium silicate, 6-8 parts of isopropyl alcohol, 0.05-0.15 parts of polyethylene glycol PEG-400, 0.02-0.08 parts of sodium citrate, 0.03-0.08 parts of beta-cyclodextrin, 0.01-0.03 parts of sodium lauryl sulfate, a surfactant, and 0.02-0.05 parts of disodium edetate, a complex stabilizer.

3. The method for preparing a textured structure suitable for a perovskite crystalline silicon tandem cell according to claim 1, wherein: The preparation method of the boron-containing ammonium hydroxide is as follows: in parts by weight, 100.0 parts of deionized water are added to a three-necked flask equipped with a stirrer, a thermometer and a gas inlet tube, ammonia gas is introduced under normal pressure to adjust the pH value of the solution to 10.0-11.0, and then 3.1-3.7 parts of boric acid are added under a stirring rate of 200.0-300.0 rpm, and the solution temperature is maintained at 25.0-30.0°C during the addition process, and then the reaction system is heated at a heating rate of 2.0-3.0°C / min to a reaction temperature of 40.0-50.0°C, and the reaction is continuously stirred at this temperature for 4.0-6.0 h to form a stable ammonium tetraborate hydroxide complex. During the reaction process, the reaction temperature is adjusted to 0.0-1.

0. The pH value was checked once and maintained stable within the range of 10.0-11.0 by adding ammonia gas. The reaction mixture was then concentrated under reduced pressure to 30.0-50.0% of the original volume. The concentrate was finally transferred to a sealed container and stored at a temperature of 2.0-6.0°C for future use.

4. The method for preparing a textured structure suitable for a perovskite silicon tandem cell according to claim 1, wherein: The silicon wafer cleaning process of step S1 includes: selecting a single crystal silicon wafer with a crystal orientation of (100) as a substrate material, the thickness of the silicon wafer is 150~200μm, placing the silicon wafer in acetone, isopropyl alcohol and deionized water for ultrasonic cleaning in turn, each cleaning time is 5~10 minutes, and then immersing the silicon wafer in a mixed solution with a volume ratio of H2SO4:H2O2=3:1, and treating it at a temperature of 80~90℃ for 10~15 minutes to remove organic pollutants, then using a hydrofluoric acid solution with a mass fraction of 1~2% to treat the silicon wafer for 30~60 seconds to remove the surface oxide layer, and finally rinsing the silicon wafer surface with a large amount of deionized water and blowing it dry with nitrogen to obtain a clean silicon wafer.

5. The method for preparing a textured structure suitable for a perovskite silicon tandem cell according to claim 1, wherein: The preparation of the velvet solution in step S2 includes: adding deionized water to a reaction vessel equipped with an agitator and a temperature control system, heating the solution temperature to 75-85°C at a stirring rate of 100-200 rpm, then adding sodium hydroxide in sequence and stirring at a stirring rate of 200-300 rpm for 10-15 minutes until completely dissolved, then adding sodium silicate and continuing to stir for 10-15 minutes to ensure uniform mixing, then adding isopropyl alcohol and stirring for 5-8 minutes, and then adding boron-containing ammonium hydroxide, polyethylene glycol PEG-400, sodium citrate, β-cyclodextrin, sodium lauryl sulfate and disodium ethylenediaminetetraacetic acid in sequence, stirring each component for 2-5 minutes after addition to ensure complete dispersion, finally keeping the mixed solution warm and stirring at a temperature of 75-85°C for 15-30 minutes to ensure sufficient complexation and equilibrium of the components, and letting it stand for 2-5 minutes to allow the solution temperature and composition to reach a stable state, thereby finally obtaining a uniform velvet solution.

6. The method for preparing a textured structure suitable for a perovskite crystalline silicon tandem cell according to claim 1, wherein: The pretreatment in step S3 includes: first, placing the cleaned silicon wafer in a diluted sodium hydroxide solution with a mass fraction of 0.1-0.3% for chemical pre-etching treatment, and the pre-etching time is 30-60 seconds; then, immersing the silicon wafer in an aqueous solution containing a mass fraction of 0.05-0.2% β-cyclodextrin, and performing surface modification treatment at 25-40° C. for a treatment time of 120-180 seconds. After the pretreatment is completed, the surface of the silicon wafer is immediately rinsed with deionized water to remove unbound β-cyclodextrin.

7. The method for preparing a textured structure suitable for a perovskite silicon tandem cell according to claim 1, wherein: The wet pyramid etching in step S4 includes: completely immersing the pretreated silicon wafer in the prepared velvet solution and ensuring that there are no bubbles attached to the surface of the silicon wafer, the immersion depth is 20-50 mm, the solution temperature is controlled at 75-80° C., the etching time is accurately controlled at 25-35 min, and the solution is stirred during the etching process at a stirring speed of 50-100 rpm using magnetic stirring.

8. The method for preparing a textured structure suitable for a perovskite silicon tandem cell according to claim 1, wherein: The subsequent cleaning and drying treatment of step S5 includes: completing the subsequent cleaning and drying treatment process, immediately removing the silicon wafer from the velvet preparation solution after etching is completed, the removal time is ≤30s, rinsing the surface of the silicon wafer with a large amount of deionized water for 3 to 5 times, each rinsing time is not less than 2 minutes, and the resistivity of the rinsing water is ≥18MΩ·cm, treating the silicon wafer with a diluted hydrochloric acid solution with a mass fraction of 1 to 3% for 30 to 60 seconds to neutralize the residual alkaline substances, and the treatment temperature is 20 to 30°C, and thoroughly rinsing the surface of the silicon wafer with deionized water again until the pH value is close to neutral, and the pH value is controlled in the range of 6.5 to 7.5, placing the silicon wafer in a vacuum drying oven at a temperature of 60 to 80°C and drying for 15 to 30 minutes, the vacuum degree is controlled at 0.1 to 1Pa, the heating rate is 2 to 5°C / min, and after drying is completed, cooling to room temperature under a nitrogen protection environment, the cooling rate is 1 to 3°C / min, and the nitrogen flow rate is 2 to 5L / min.

9. A velvet structure suitable for perovskite crystalline silicon tandem cells prepared by the method for preparing a velvet structure suitable for perovskite crystalline silicon tandem cells according to claims 1 to 8, characterized in that: The velvet structure is composed of a large number of regularly arranged and uniformly sized tetrahedral pyramid units, and the base angle θp of each pyramid unit is an average of 45° to 60°; The average length of the base of the pyramid is 2 μm to 6 μm; The average ratio of the pyramid height to the base length is 0.5 to 0.9; The average distribution density of the pyramids on the silicon substrate is 1×10 6 ~2×10 7 pieces / cm 2 .

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