A high-purity fluoride salt, its preparation method and application

Abstract

This invention relates to the field of fluoride salt technology, and more particularly to a high-purity fluoride salt, its preparation method, and its applications. The high-purity fluoride salt has a purity of not less than 99.999%. When combined with chalcone derivatives, it forms a photoelectric device modification layer that effectively controls the wettability of perovskite precursor solutions and induces growth through a template effect, ultimately yielding a perovskite film with high crystallinity and a smooth surface. The high-purity fluoride salt effectively avoids impurities and defects, promoting the orderly anchoring of organic molecules to form an ordered structure, thereby achieving efficient interface passivation and charge transport, and improving carrier mobility. The composite modification layer formed by the chalcone derivatives and the high-purity fluoride salt constructs a stable interface, effectively inhibiting ion migration and decomposition, and significantly extending the device's operating life.

Description

Technical Field

[0001] This invention relates to the field of fluoride salt technology, and in particular to a high-purity fluoride salt, its preparation method, and its application. Background Technology

[0002] With the rapid development of the new energy industry and optoelectronic technology, various optoelectronic thin-film devices such as solar cells, light-emitting diodes, and photodetectors have become core components driving the upgrading of related industries. In the structure of these optoelectronic thin-film devices, the photoactive layer is responsible for photon absorption and carrier generation, while the charge transport layer is responsible for the efficient transport and separation of photogenerated carriers. The interface between the two is a key channel for carrier transport, and its interface state has a significant impact on the carrier transport efficiency and recombination loss, which is crucial to determining the performance and stability of optoelectronic devices.

[0003] However, in the actual fabrication process, defects and dangling bonds inevitably exist at the interface between the charge transport layer and the photoactive layer. These interface states can cause severe nonradiative recombination, resulting in a large loss of photogenerated carriers. At the same time, they can also promote ion migration, destroy the stability of the device interface, and thus limit the efficiency improvement and lifetime extension of optoelectronic thin film devices, thus restricting the development of optoelectronic thin film devices towards high performance and long lifetime.

[0004] High-purity inorganic fluorides possess excellent stability, suitable energy levels, and good defect passivation capabilities, making them a promising class of interface modification materials. However, the purity and morphology of the fluoride material, as well as its interaction mechanism with the underlying substrate and the upper active layer, play a crucial role in the final modification effect.

[0005] Currently, for upright perovskite solar cells, although fluoride intercalation can improve charge transport, it can affect the wetting and crystallization of the subsequent perovskite precursor solution, leading to a decrease in film quality and limiting the efficiency improvement capability of the fluoride passivation layer.

[0006] Perovskite materials, due to their long carrier diffusion length and high absorption coefficient, are among the mainstream materials for photoactive layers. Currently, inorganic fluorides are commonly used for interface modification because of their simple preparation process and low cost, and have been applied to some extent in perovskite optoelectronic thin film devices. However, in practical applications, it has been found that the technical defects of traditional inorganic fluoride modification layers have adversely affected the film quality of perovskite layers. These technical defects are mainly reflected in the following aspects:

[0007] Firstly, inorganic fluorides have low surface energy and poor polarity matching with perovskite precursors, resulting in poor wettability between the perovskite precursor and the modification layer. This makes it easy for problems such as edge shrinkage and agglomeration to occur during coating, making it difficult to form a uniform and continuous perovskite film.

[0008] Secondly, inorganic fluorides may interact adversely with perovskite precursors, thereby inhibiting perovskite grain growth, reducing the crystallinity of the perovskite layer, and causing a large number of grain boundary defects inside the perovskite film.

[0009] Third, poor wettability and low crystallinity will exacerbate the interface defect density between the charge transport layer and the perovskite layer, increase the carrier recombination channels, and cause a significant increase in nonradiative recombination loss, making ion migration more pronounced.

[0010] Therefore, improving the purity of fluoride salts and developing efficient interface modification materials and technologies to achieve effective passivation of interface defects, precise optimization of energy level arrangement, and high-quality crystallization induction of photoactive layers are urgent technical problems that need to be solved. Summary of the Invention

[0011] This invention aims to at least solve one of the technical problems existing in related technologies. Therefore, the first objective of this invention is to provide an application of a high-purity fluoride salt; the second objective is to provide a method for preparing a high-purity fluoride salt; and the third objective is to provide a high-purity fluoride salt.

[0012] To achieve the first objective, the technical solution adopted by this invention is as follows:

[0013] An application of a high-purity fluoride salt, wherein the purity of the high-purity fluoride salt is ≥99.999%, is used to prepare a modification layer for optoelectronic devices, comprising the following steps:

[0014] S100. Zinc oxide electron transport layer is prepared using precursor solution I containing zinc salt and magnesium salt;

[0015] The molar ratio of the zinc salt to the magnesium salt is (2.5–4.5):1;

[0016] S200. Using vacuum evaporation technology, the high-purity fluoride salt is deposited on the surface of the zinc oxide electron transport layer to obtain a passivation layer.

[0017] S300. The passivation layer is immersed in a chalcone derivative solution to anchor the molecules of the chalcone derivative to the surface of the passivation layer, thereby obtaining a photoelectric device modification layer.

[0018] The structural formula of the chalcone derivative is shown below:

[0019] .

[0020] Metallic impurities in traditional fluorides can form defect sites during deposition, disrupting the passivation layer's deposition effect. High-purity fluoride salts (≥99.999%) of 5N grade almost completely remove these harmful impurities, ensuring the orderly anchoring of organic molecules and providing a chemically pure interface for perovskite growth, thus avoiding heterogeneous nucleation. Furthermore, the cyano groups at the ends of chalcone derivative molecules are tightly linked to the high-purity inorganic fluoride on the substrate via weak coordination bonds, promoting the directional anchoring of organic molecules at the fluorination interface, forming a molecular-level ordered arrangement rather than random stacking. This ensures efficient charge transport between perovskite and inorganic fluoride intercalation. Simultaneously, chalcone derivatives can moderately regulate the spreading behavior of the perovskite precursor solution on the modified layer, achieving controllable wettability by balancing intermolecular forces, effectively avoiding excessive repulsion caused by inorganic fluorides.

[0021] Further, in step S100, the zinc salt is selected from zinc acetate dihydrate, and the magnesium salt is selected from magnesium acetate tetrahydrate.

[0022] Further, in step S100, the solvent of the precursor solution I is selected from tetrahydrofuran and / or acetonitrile.

[0023] Furthermore, in step S200, the thickness of the passivation layer is 0.5 nm to 1 nm.

[0024] Further, in step S300, the concentration of the chalcone derivative solution is 1 mg / mL to 7 mg / mL.

[0025] Furthermore, in step S300, the solvent for the chalcone derivative solution is selected from alcohol solvents.

[0026] To achieve the second objective, the technical solution adopted by this invention is as follows:

[0027] A method for preparing a high-purity fluoride salt, wherein the high-purity fluoride salt described in any of the above-mentioned methods is CaF2, comprises the following steps:

[0028] S10. Under stirring conditions, add ammonium carbonate aqueous solution to calcium chloride aqueous solution at a rate of 5-10 mL / min to react calcium chloride with ammonium carbonate to form calcium carbonate precipitate. The calcium carbonate precipitate is filtered, washed with water and ethanol in sequence and then dried to obtain calcium carbonate solid.

[0029] S20. Grind the calcium carbonate solid into powder using a mortar and pestle, and then sieve it through a 1000-3000 mesh sieve to obtain calcium carbonate powder.

[0030] S30. The calcium carbonate powder is added to a 35wt%–45wt% hydrofluoric acid aqueous solution, stirred and the reaction system is maintained at 20–25°C. After stirring for 30–60 min, the mixture is allowed to stand for 15–25 min and then filtered. The resulting filter cake is washed sequentially with hydrofluoric acid aqueous solution, water, and ethanol, and then dried and ground to obtain calcium fluoride powder A. The purity of the calcium fluoride powder A is ≥99.9%.

[0031] S40. The calcium fluoride powder A is purified using zone melting technology to obtain the high-purity fluoride salt.

[0032] Furthermore, the zone melting technique in step S40 is processed as follows:

[0033] The calcium fluoride powder A was added to a sample tube, which was then placed in a melting furnace chamber at 290℃~310℃ and 1×10⁻⁶. -4 After the calcium fluoride powder A is subjected to preliminary impurity removal for 3-5 hours under the condition of Pa, nitrogen gas is introduced into the melting furnace cavity to atmospheric pressure. Then, one end of the sample tube is heated to 1390-1410°C at a heating rate of 5-10°C / min and maintained for 30-60 minutes. The melting zone is then slowly moved to the other end of the sample tube at a speed of 2.5-3.5 mm / h. After the melting zone reaches the end of the sample tube, heating is stopped and the sample is cooled to room temperature. The sample is then removed from the sample tube, and the middle 1 / 3 section of the sample crystal column is cut out with a diamond wire saw. After grinding with a crusher, the high-purity fluoride salt is obtained.

[0034] Furthermore, the sample tube is made of graphite.

[0035] To achieve the third objective, the technical solution adopted by this invention is as follows:

[0036] A high-purity fluoride salt is prepared using any one of the methods described above.

[0037] The above-described one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0038] This invention provides a high-purity fluoride salt, its preparation method, and its applications. The purity of the high-purity fluoride salt is not less than 99.999%. A photoelectric device modification layer prepared by combining it with chalcone derivatives can effectively control the wettability of perovskite precursor solutions and induce growth through a template effect, ultimately yielding a perovskite thin film with high crystallinity and a smooth surface. The high-purity fluoride salt can effectively avoid impurities and defects, promoting the orderly anchoring of organic molecules to form an ordered structure, thereby achieving efficient interface passivation and charge transport, and improving carrier mobility. The composite modification layer formed by chalcone derivatives and high-purity fluoride salt constructs a stable interface, effectively inhibiting ion migration and decomposition, and significantly extending the device's operating life.

[0039] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0040] Figure 1 This is the proton nuclear magnetic resonance spectrum of the chalcone derivatives provided in Example 2 of the present invention ( 1 H NMR).

[0041] Figure 2 This is a diagram showing the test results of FTO / ZnO / CaF2 / CDs, FTO / ZnO / CaF2, and FTO / ZnO contact angles provided in the test examples of this invention.

[0042] Figure 3 These are scanning electron microscope (SEM) images of perovskite thin films based on FTO / ZnO / CaF2 / CDs, FTO / ZnO / CaF2, and FTO / ZnO provided in the detection examples of this invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. The following embodiments are used to illustrate this invention, but cannot be used to limit the scope of this invention.

[0044] In the following embodiments, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available, unless otherwise specified, and are carried out in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions.

[0045] Example 1

[0046] The process for preparing CaF2 with a purity of not less than 99.999% is as follows:

[0047] Calcium chloride (150g) and water (300mL) were added sequentially to a three-necked flask and stirred until completely dissolved. Then, under stirring, ammonium carbonate aqueous solution (a solution prepared by dissolving 189g of ammonium carbonate in 250mL of water) was slowly added at a rate of 5–10mL / min. The reaction produced calcium carbonate precipitate, which was filtered, washed with water and ethanol, and then dried to obtain calcium carbonate (130g). The calcium carbonate was ground into powder using a mortar and pestle and sieved through a 2000-mesh sieve to obtain calcium carbonate powder. Subsequently, in a fume hood, the powder was added at a rate of 0.5–2g / min. The calcium carbonate powder was slowly added to a 40wt% hydrofluoric acid aqueous solution (250mL) and stirred continuously. The reaction system temperature was maintained at 20-25℃. The reaction was stirred until no bubbles were generated (about 30-60min). After standing for 20min, the mixture was filtered through a polypropylene filter to obtain a filter cake. The filter cake was first washed with a 20wt% hydrofluoric acid aqueous solution (30mL), then washed with water until neutral, and then washed with ethanol. After drying in an oven and grinding in a mortar, it was placed in a vacuum drying oven (dried at 100℃ for 10h) to obtain calcium fluoride powder A (100g) (purity of 99.97%, which is >3N).

[0048] Calcium fluoride powder A was further purified using a zone melting furnace, as follows: 70g of calcium fluoride powder A was placed into a graphite sample tube and placed horizontally in the zone melting furnace chamber; first, it was purified at 300℃ and 1×10⁻⁶ ppm. -4 Under the condition of Pa, the entire sample was initially purified for 3-5 hours (to remove volatile impurities); then nitrogen gas was introduced into the chamber to atmospheric pressure, and one end of the sample tube was heated to 1400℃ at a rate of 5-10℃ / min and maintained for 30-60 minutes. The molten zone was then slowly moved to the other end at a speed of 3 mm / h. When the molten zone reached the end of the sample tube, heating was stopped and the sample was cooled to room temperature. The sample was removed from the sample tube, and the middle 1 / 3 section of the sample crystal column was cut out with a diamond wire saw. The sample was then ground with a crusher to obtain high-purity calcium fluoride powder B (purity of 99.9992%, which is >5N).

[0049] The testing procedures for calcium fluoride powder A and calcium fluoride powder B are as follows:

[0050] Weigh 0.2–0.3 g of calcium fluoride powder (calcium fluoride powder A or calcium fluoride powder B) to an accuracy of 0.0001 g, add HNO3 aqueous solution (2 mol / L, 3 mL), then add H3BO3 aqueous solution (40 g / L, 3 mL), and place in a microwave digester (400 W, 10 min) for digestion. After digestion, add deionized water (30 mL) to obtain the test solution.

[0051] Using the exact same reagent dosage, operating steps, and digestion procedure as described above, but without adding calcium fluoride powder A or calcium fluoride powder B, a blank solution was prepared simultaneously to subtract background impurities introduced by reagents, experimental instruments, and the environment.

[0052] The test solution and blank solution were analyzed using inductively coupled plasma atomic emission spectrometry (ICP-MS) to determine the content of various ionic impurities. The results are shown in Tables 1 and 2.

[0053] Table 1. Content of various impurities in calcium fluoride powder A

[0054]

[0055] Table 2. Content of various impurities in calcium fluoride powder B

[0056]

[0057] The purity of calcium fluoride powder is calculated using the difference method, i.e., CaF2 purity = 100% - the sum of the measured values ​​of all metallic impurity elements.

[0058] Based on the data provided in Table 1, the purity of calcium fluoride powder A is calculated to be 99.97%; based on the data provided in Table 2, the purity of calcium fluoride powder B is calculated to be 99.9992%.

[0059] Example 2

[0060] Preparation of chalcone derivatives The process is as follows:

[0061] 4-Acetylbenzonitrile (1.0 mmol) and 5-formylisophthalonitrile (1.0 mmol) were added to a dry round-bottom flask, followed by the addition of anhydrous ethanol (10 mL) and stirring to dissolve. Then, 1.2 mmol of solid potassium hydroxide was added, a magnetic stir bar was attached, and a reflux condenser was connected. The mixture was heated in an oil bath, slowly raised to 60 °C, and stirred under reflux for 10 h. Deionized water (20 mL) was added to the reaction mixture, and the crude solid product was collected by filtration. This crude product was then purified by recrystallization from dichloromethane to obtain the target chalcone derivative, denoted as CDs. 1 H NMR, such as Figure 1 As shown, the specific characterization data is as follows:

[0062] 1H NMR (400MHz, CDCl3): δ=8.73 (d, J=1.7, 2H), 8.69 (t, J=1.8, 1H), 8.07-8.05 (m, 2H), 7.85-7.83 (m, 2H), 7.78 (d, J=15.7, 1H), 6.74 (d, J=15.7, 1H).

[0063] Example 3

[0064] Battery devices were prepared in control groups 1, 2, and 3, as well as sample 1, sample 2, sample 3, and sample 4. The structures of each group of devices are shown below:

[0065] Control group 1: FTO / ZnO / perovskite / P3HT / Au;

[0066] Control group 2: FTO / ZnO / CaF2 / perovskite / P3HT / Au;

[0067] Control group 3: FTO / ZnO / CDs / perovskite / P3HT / Au;

[0068] Control group 4, experimental groups 1, 2, 3, 4: FTO / ZnO / CaF2 / CDs / perovskite / P3HT / Au, (where CaF2 / CDs is referred to as the composite layer);

[0069] In the control group 4, the CaF2 layer was prepared using calcium fluoride powder A, while the CaF2 layers in experimental groups 1, 2, 3, and 4 were prepared using calcium fluoride powder B. The concentrations of the CDs solutions used to prepare the CDs layers in experimental groups 1, 2, 3, and 4 were 1 mg / mL, 3 mg / mL, 5 mg / mL, and 7 mg / mL, respectively.

[0070] I. Fabrication of battery devices (control group 1), the specific steps are as follows:

[0071] Step 1: Treat the fluorine-doped tin oxide (FTO) conductive glass substrate.

[0072] FTO conductive glass was selected as the substrate, and a preset electrode pattern was etched on the substrate surface using a laser marking system. After etching, the substrate surface was purged with nitrogen to remove particulate impurities and etching debris. Subsequently, the etched and purged substrate was placed in glass cleaning solution, deionized water, acetone, ethanol, and isopropanol in sequence. Each step was treated with ultrasonic cleaning for 20 minutes. After ultrasonic cleaning, the substrate was placed in an oven and dried at 75°C for 1 hour to completely remove residual organic solvents from the substrate surface, resulting in a clean and dry FTO conductive glass substrate.

[0073] Step 2: Prepare the ZnO electron transport layer.

[0074] Preparation of electron transport layer precursor solution: Add zinc acetate dihydrate (50 mg) and magnesium acetate tetrahydrate (16.3 mg) to a mixed solvent of tetrahydrofuran and acetonitrile (volume ratio 10:1) (5 mL), stir at room temperature (about 25 °C) for 30 min until completely dissolved to obtain electron transport layer precursor solution.

[0075] Formation of the electron transport layer: The clean and dry FTO conductive glass substrate was treated with a UV ozone cleaner for 20 min. Then, 500 μL of electron transport layer precursor solution was uniformly dropped onto the substrate surface and spin-coated at 3000 rpm for 25 s. After spin-coating, the substrate was placed on a heating plate and the temperature was set to 100℃. After annealing for 10 min, the substrate was slowly transferred to a muffle furnace and the heating rate was set to 5℃ / min. The temperature was raised to 400℃ and maintained at this temperature for sintering for 30 min. After sintering, the substrate was naturally cooled to room temperature (cooling rate 2℃ / min). A ZnO electron transport layer with a thickness of about 100 nm (denoted as FTO / ZnO) was formed on the surface of the FTO substrate.

[0076] Step 3: Prepare perovskite thin films.

[0077] 1. Preparation of perovskite precursor solution: Add CsI, FAI and PbI2 in a molar ratio of 1:9:10 to a mixed solvent of DMF and DMSO (volume ratio 4:1), stir until completely dissolved, and prepare a solution with a PbI2 component concentration of 1.3 mol / L, labeled as solution A;

[0078] Take equal amounts of MABr and PbBr2, dissolve them in a mixed solvent of DMF and DMSO (volume ratio 4:1), stir until completely dissolved, and prepare a solution with a PbBr2 component concentration of 1.3 mol / L, labeled as solution B;

[0079] Solution A and solution B were mixed at a volume ratio of 19:1 and stirred at room temperature for 30 minutes until fully homogeneous, yielding a perovskite precursor solution with a concentration of 1.3 mol / L. The perovskite component corresponding to this perovskite precursor solution was MA. 0.05 (Cs 0.1 FA 0.9 ) 0.95 Pb(I 0.95 Br 0.05 3.

[0080] 2. Preparation of perovskite thin film: Under nitrogen atmosphere, a perovskite precursor solution (60 μL) was dropped onto the electron transport layer. The film was first spin-coated at 800 rpm for 15 s, and then at 4500 rpm for 25 s. 10 s before the end of spin-coating, toluene (0.25 mL) was added as an antisolvent to precipitate perovskite crystals. Immediately after spin-coating, the substrate with perovskite crystals was transferred to a hot plate and annealed at 110 °C for 40 min to obtain a black perovskite thin film.

[0081] Step 4: Prepare the hole transport layer.

[0082] Poly(3-hexylthiophene) (P3HT) (10 mg) was dissolved in chlorobenzene (1 mL), sealed, and heated in a water bath at 50 °C for 10 min to promote dissolution, thus obtaining a P3HT solution. Subsequently, 500 μL of this solution was rapidly dropped onto the surface of the perovskite film layer when spin-coating a substrate with a perovskite film at a spin-coating speed of 5000 rpm. After the droplet was finished, spin-coating was continued for 30 s. After spin-coating was completed, the film was allowed to air dry for 30 min, thus forming a hole transport layer with a thickness of approximately 100 nm on the surface of the perovskite film.

[0083] Step 5: Deposit metal electrode.

[0084] The substrate with the hole transport layer is placed in a vacuum evaporation apparatus, maintaining a pressure of 1×10⁻⁶. -4 Pa, the metal target was heated until it melted, and an Au electrode was deposited on the surface of the hole transport layer at a deposition rate of 0.05 nm / s. The electrode thickness was monitored in real time by a film thickness monitor. An Au electrode with a thickness of 800 nm was deposited. After deposition, the electrode was removed and allowed to cool naturally to room temperature, thus completing the preparation of the control group 1 battery device.

[0085] II. Preparation of battery devices (Experimental Group 1, Experimental Group 2, Experimental Group 3 and Experimental Group 4).

[0086] The main differences between the experimental group battery device and the control group 1 battery device are as follows: a CaF2 / CDs composite layer was added between the ZnO electron transport layer and the perovskite thin film. The rest of the process was the same as that of the control group 1 battery device.

[0087] The preparation of the CaF2 / CDs composite layer includes the following steps:

[0088] 1. Fluoride passivation layer deposition:

[0089] After the ZnO electron transport layer is prepared, the substrate with the ZnO electron transport layer is placed in a vacuum evaporation apparatus and the pressure is maintained at 1×10⁻⁶. -4Pa, fluoride powder B is heated, and a fluoride passivation layer with a thickness of about 0.75 nm is deposited on the surface of the ZnO electron transport layer at a deposition rate of 0.02 nm / s to obtain a substrate (FTO / ZnO / CaF2) with a fluoride passivation layer.

[0090] 2. Preparation of organic-assisted wetting layer.

[0091] CDs methanol solutions of 1 mg / mL (experimental group 1), 3 mg / mL (experimental group 2), 5 mg / mL (experimental group 3), and 7 mg / mL (experimental group 4) were prepared respectively.

[0092] The substrate with the fluoride passivation layer was immersed in a 1 mg / mL CDs methanol solution and kept immersed at 70 °C for 15 min to obtain a substrate with a CaF2 / CDs composite layer (experimental group 1).

[0093] The substrate with the fluoride passivation layer was immersed in a 3 mg / mL CDs methanol solution and kept immersed at 70°C for 15 min to obtain a substrate with a CaF2 / CDs composite layer (experimental group 2).

[0094] The substrate with the fluoride passivation layer was immersed in a 5 mg / mL CDs methanol solution and kept immersed at 70 °C for 15 min to obtain a substrate with a CaF2 / CDs composite layer (experimental group 3), denoted as FTO / ZnO / CaF2 / CDs;

[0095] The substrate with the fluoride passivation layer was immersed in a 7 mg / mL CDs methanol solution and kept immersed at 70 °C for 15 min to obtain a substrate with a CaF2 / CDs composite layer (experimental group 4).

[0096] II. Fabrication of battery devices (control group 2).

[0097] To demonstrate the necessity of introducing CDs molecules, this group deposited a 0.75 nm thick calcium fluoride powder B passivation layer after preparing the ZnO electron transport layer, but did not introduce CDs. The remaining steps were the same as those in control group 1.

[0098] III. Preparation of battery devices (control group 3).

[0099] To demonstrate the anchoring effect of CDs molecules on the fluoride passivation layer, this group only immersed the prepared ZnO electron transport layer in a 5 mg / mL CDs solution, and the remaining steps were the same as those in control group 1.

[0100] IV. Preparation of battery devices (control group 4).

[0101] To investigate the effect of fluorides of different purities on the performance of the final battery device, this group differed from the battery device (experimental group 3) in that the fluoride powder B used to prepare the fluoride passivation layer was replaced with fluoride powder A, while the remaining steps were the same as those in experimental group 3.

[0102] Detection example

[0103] I. Determination of contact angle.

[0104] To verify that CDs molecules can adsorb onto fluoride surfaces and improve the wettability of perovskite precursor solutions on substrates, contact angle measurements were performed on the surfaces of FTO / ZnO (control group 1), FTO / ZnO / CaF2 (control group 2), and FTO / ZnO / CaF2 / CDs (experimental group 3) after dropping perovskite precursor solutions onto the substrates. The results are as follows: Figure 2 As shown in the figure, fluoride slightly affects the wettability of the perovskite precursor solution on the substrate. However, the introduction of CDs molecules onto the fluoride surface significantly improves the wettability of the perovskite precursor, making it easier to spread during spin coating and thus forming a higher quality perovskite film. This result indicates that through the immersion process, CDs molecules can adsorb onto the fluoride surface to assist in the spreading of the perovskite solution.

[0105] II. Microscopic morphology.

[0106] To further confirm the role of CDs molecules in improving the quality of perovskite films, SEM measurements were performed on perovskite films based on three substrates: FTO / ZnO (control group 1), FTO / ZnO / CaF2 (control group 2), and FTO / ZnO / CaF2 / CDs (experimental group 3). The results are as follows: Figure 3 As shown in the figure, the perovskite films based on FTO / ZnO and FTO / ZnO / CaF2 have similar crystal morphologies, exhibiting a three-dimensional accumulation of grains on the surface, with relatively small grain sizes leading to a high number of grain boundaries. In contrast, the perovskite film based on the FTO / ZnO / CaF2 / CDs substrate shows a significantly larger grain size, reducing the formation of grain boundaries. This result indicates that the CDs organic molecules provide a favorable environment for perovskite solution spreading, making the grain growth process in the perovskite film preparation more regular.

[0107] III. Performance testing of battery devices with different structures.

[0108] The battery efficiency testing process is as follows: Before testing, a standard silicon solar cell is first used to calibrate the simulated sunlight to achieve an irradiance of AM 1.5G. Under this condition, the JV curve of the battery device is tested, and the open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), and power conversion efficiency (PCE) performance data of the battery are obtained after software fitting, as shown in Table 3.

[0109] Table 3 Battery efficiency test results

[0110]

[0111] Table 3 shows that the performance improvement of control group 2 (FTO / ZnO / CaF2 / perovskite / P3HT / Au) compared to control group 1 (FTO / ZnO / perovskite / P3HT / Au) is limited, while the efficiency of control group 3 (FTO / ZnO / CDs / perovskite / P3HT / Au) is slightly lower than that of the baseline control group 1. These comparisons indicate that the composite layer formed by the synergistic effect of CaF2 and CDs molecules significantly improves battery performance. Furthermore, in terms of battery efficiency, experimental group 3 has the highest PCE, indicating that the optimal immersion concentration of CDs is 5 mg / mL. In addition, comparisons between the experimental group and control groups 1 and 4 show that while using lower purity CaF2 (3N < purity < 5N) as the composite layer for this strategy can slightly improve efficiency, it is significantly less efficient than using high purity CaF2 (purity ≥ 5N), indicating that the high concentration of ionic impurities hinders charge transport.

[0112] To characterize the effect of the composite layer on charge transport in the device, the hole mobility (μ) of the thin film was measured. Using an electrochemical workstation, the space charge-confined carrier method (SCLC) was employed to test the battery device under dark conditions. The results are shown in Table 4.

[0113] Table 4. Results of thin film hole mobility test

[0114]

[0115] Table 4 shows that the charge transport performance of control group 4, which uses low-purity CaF2 as the modification layer, is significantly worse than that of the experimental group using high-purity CaF2. This result indicates that impurities in fluoride salts are a significant factor affecting charge transport. The charge transport capability of control group 2 (FTO / ZnO / CaF2 / perovskite / P3HT / Au) is significantly improved compared to control group 1 (FTO / ZnO / perovskite / P3HT / Au). Moreover, the charge transport capability is further enhanced after introducing CDs molecules into the CaF2 interface of experimental groups 1–4. Furthermore, in control group 2, it is evident that directly introducing CDs molecules to the electron transport layer surface leads to poor interactions, even exhibiting negative effects, thus adversely impacting the charge transport performance of the battery device.

[0116] Under the influence of external factors such as light and heat, defects at the interface are prone to migration, inducing phase separation in the perovskite and ultimately leading to lattice structure disorder, resulting in a continuous decline in battery efficiency. To test and evaluate the effect of this composite layer on interface defects, the stability of each group of battery devices under light and high temperature was tested. Different groups of battery devices were placed in a nitrogen atmosphere at 80°C and continuously irradiated with AM 1.5G light intensity for 1000 hours, with JV curve tests performed every 250 hours to track their efficiency. The normalized initial efficiency data are shown in Table 5.

[0117] Table 5 Results of optical and thermal stability tests

[0118]

[0119] Table 5 shows that after 1000 hours of aging, the battery device stability of control group 2 (using only high-purity CaF2 as a passivation layer) was significantly improved compared to control group 1. After introducing CDs molecules, experimental group 3 exhibited the best lifespan performance, maintaining an efficiency above 90% of its initial value before aging. This indicates that the introduction of CDs molecules at the interface further reduced interface defects and significantly slowed down the irreversible degradation process of the perovskite film caused by interface defects under external stress. The results of control group 3 show that introducing only CDs molecules negatively impacts battery lifespan. This is because CDs molecules are incompatible with the ZnO interface, leading to molecular desorption at high temperatures and adversely affecting the internal structure of the perovskite. Furthermore, comparing control group 4 with the experimental group reveals that while the strategy of introducing a fluoride composite layer significantly improves battery lifespan, the improvement in stability is more pronounced with high-purity fluoride salt raw materials. This indicates that the purity of fluoride salts is a key parameter determining battery performance.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. The application of a high-purity fluoride salt in optoelectronic devices, characterized in that, The high-purity fluoride salt has a purity ≥99.999%, and the high-purity fluoride salt is CaF2. The preparation of a photoelectric device modification layer using the high-purity fluoride salt includes the following steps: S100. Zinc oxide electron transport layer is prepared using precursor solution I containing zinc salt and magnesium salt; The molar ratio of the zinc salt to the magnesium salt is (2.5–4.5):1; S200. Using vacuum evaporation technology, the high-purity fluoride salt is deposited on the surface of the zinc oxide electron transport layer to obtain a passivation layer. S300. The passivation layer is immersed in a chalcone derivative solution to anchor the molecules of the chalcone derivative to the surface of the passivation layer, thereby obtaining a photoelectric device modification layer. The structural formula of the chalcone derivative is shown below: 。 2. The application of the high-purity fluoride salt in optoelectronic devices as described in claim 1, characterized in that, In step S100, the zinc salt is selected from zinc acetate dihydrate, and the magnesium salt is selected from magnesium acetate tetrahydrate.

3. The application of the high-purity fluoride salt in optoelectronic devices as described in claim 1, characterized in that, In step S100, the solvent of the precursor solution I is selected from tetrahydrofuran and / or acetonitrile.

4. The application of the high-purity fluoride salt as described in claim 1 in optoelectronic devices, characterized in that, In step S200, the thickness of the passivation layer is 0.5 nm to 1 nm.

5. The application of the high-purity fluoride salt as described in claim 1 in optoelectronic devices, characterized in that, In step S300, the concentration of the chalcone derivative solution is 1 mg / mL to 7 mg / mL.

6. The application of the high-purity fluoride salt as described in claim 1 in optoelectronic devices, characterized in that, In step S300, the solvent for the chalcone derivative solution is selected from alcohol solvents.

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