High-purity cesium iodide as well as preparation and application thereof

Abstract

The invention provides high-purity cesium iodide as well as a preparation method and application thereof. The preparation method comprises the following steps: S1, carrying out alkali adjustment on lithium ore lithium-extracted liquid, carrying out multi-stage counter-current extraction by adopting an extraction agent and a diluent, and selectively separating cesium ions to obtain a cesium-loaded organic phase; s2, washing the cesium-loaded organic phase with a hydroiodic acid solution, and removing co-extracted impurity ions such as K < + > and Na < + >; s3, a hydriodic acid solution is adopted as a stripping agent for reverse extraction, and cesium-rich strip liquor is obtained; s4, the cesium-rich strip liquor is subjected to oil removal treatment through macroporous adsorption resin; s5, carrying out primary rotary evaporation concentration and secondary freezing crystallization on the deoiled solution, and then carrying out suction filtration to obtain a CsI solid; s6, washing the CsI solid with an anti-solvent to remove free iodine; and S7, roasting the washed CsI in a certain atmosphere at 550-650 DEG C to obtain the high-purity cesium iodide powder.

Description

Technical Field

[0001] This application relates to the field of high-purity cesium iodide technology, and more particularly to a high-purity cesium iodide, its preparation and application. Background Technology

[0002] In recent years, with the rapid development of the new energy industry, the demand for lithium resources has increased dramatically. During the lithium extraction process from lithium ores (such as spodumene and lepidolite), a large amount of waste liquid or residue containing valuable metals such as rubidium and cesium is generated. Cesium (Cs), as a rare alkali metal, has significant application value in high-tech fields, especially in perovskite solar cells (PSCs). Cesium iodide (CsI) is widely used as an interface modification layer or additive due to its excellent photoelectric properties and stability, in order to improve the efficiency and long-term stability of the cells.

[0003] Currently, industrial methods primarily employ solvent extraction, ion exchange, or precipitation to recover cesium from lithium extraction liquids. However, existing technologies suffer from the following problems: 1. Low recovery rate: Traditional methods have low cesium recovery rates and struggle to effectively separate associated metals such as rubidium (Rb), leading to resource waste; 2. Insufficient purity: Purified cesium compounds often contain impurities such as sodium, potassium, and lithium, failing to meet the requirements of perovskite solar cells for high-purity cesium iodide (≥99.995%); 3. High energy consumption and cost: Some processes involve multiple crystallization and high-temperature calcination steps, resulting in high production costs and hindering industrial-scale promotion; 4. Waste liquid treatment issues: Existing methods do not adequately utilize lithium extraction waste liquids, easily causing environmental pollution. Therefore, developing an efficient, low-cost, and high-purity method for cesium sulfate recovery and cesium iodide preparation, and applying it to perovskite solar cells, has significant economic and environmental value. The present invention aims to solve the above-mentioned technical problems and provide a green and efficient process for cesium resource recovery and high-purity cesium iodide preparation, so as to promote the comprehensive utilization of lithium mineral resources and the development of the perovskite photovoltaic industry. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned problems by providing a high-purity cesium iodide, its preparation, and its application.

[0005] The technical solution of this application is implemented as follows: This invention provides a method for preparing high-purity cesium iodide, comprising the following steps: S1, after lithium extraction from lithium ore, the alkali is adjusted, and multi-stage countercurrent extraction is performed using an extractant and a diluent to selectively separate cesium ions and obtain a cesium-loaded organic phase; S2, the cesium-supported organic phase is washed with hydroiodic acid solution to remove co-extracted K. + Na + Impurity ions; S3, using hydroiodic acid solution as the back-extraction agent, back-extraction is performed to obtain a cesium-rich back-extraction solution; S4, the cesium-rich back-extraction solution is de-oiled by passing it through a macroporous adsorption resin; S5, after oil removal, the solution is concentrated by rotary evaporation once and then frozen and crystallized twice before being filtered to obtain solid CsI; S6, CsI solid is washed with an anti-solvent to remove free iodine; S7. The washed CsI is calcined at 550~650℃ under a certain atmosphere to obtain high-purity cesium iodide powder.

[0006] As a further improvement, in step S1, the alkali adjustment is to adjust the pH value of the lithium ore extraction solution to 13.3~14.5.

[0007] As a further improvement, in step S1, the extractant is 4-tert-butyl-2-(α-methylbenzyl)phenol (t-BAMBP), and the diluent is one or more of sulfonated kerosene, diethylbenzene, and liquid paraffin.

[0008] As a further improvement, the O / A ratio for multi-stage countercurrent extraction is 1.8~2.2:1.

[0009] As a further improvement, in step S2, the cesium-supported organic phase is washed with a 0.010~0.005 mol / L hydroiodic acid solution.

[0010] As a further improvement, in step S3, the cesium-carrying organic phase is washed with a 0.90~0.95mol / L hydrogen iodide solution and subjected to three-stage countercurrent back-extraction. The washed cesium-carrying organic phase and the hydrogen iodide solution are mixed at a volume ratio of 10~20:1, and after phase separation and clarification, a cesium-rich solution is obtained.

[0011] As a further improvement, in step S6, the unreacted free iodine is dissolved by washing with one or more antisolvents selected from ethanol, isopropanol, acetone, benzene, or carbon tetrachloride.

[0012] As a further improvement, the present invention provides a high-purity cesium iodide, which is obtained by the above-described method.

[0013] As a further improvement, the present invention further provides an application of the above-mentioned high-purity cesium iodide in perovskite batteries.

[0014] The advantages or beneficial effects of the above technical solutions include at least the following: This invention discloses a method for recovering cesium sulfate from lithium ore post-lithium extraction liquid and purifying it to prepare perovskite solar cell-grade cesium iodide. The invention employs an optimized process flow: extraction and separation → washing → back-extraction → resin degreasing → gradient concentration (primary concentration → secondary concentration) → anti-solvent purification → calcination and drying → high-purity cesium iodide product. This process has the following technical advantages: (1) By introducing resin degreasing process, the organic content in the system is effectively reduced (TOC≤5ppm, COD≤10ppm), and the purity of the product is significantly improved; (2) The gradient concentration technology (concentrating to 70-90% in one step and to 85-95% in two steps) is adopted to improve the cesium ion enrichment efficiency by more than 10%; (3) Innovative anti-solvent removal process is adopted to selectively remove iodide impurities (removal rate > 95%). (4) Optimize the roasting process (300-700℃) to accurately control the iodine content and avoid excessive iodine residue; (5) The obtained high-purity cesium iodide (purity ≥ 99.995%) can be directly used in the preparation of perovskite solar cells, and the comprehensive utilization rate of cesium resources is over 90%; (6) The high-purity cesium iodide prepared in this invention is used as a key functional material in the preparation of perovskite solar cells. Compared with commercially available cesium iodide products, it can significantly improve the photoelectric performance of the device, effectively improve the crystal quality of the perovskite film, optimize the energy level matching, and thus prepare perovskite solar cell devices with higher photoelectric conversion efficiency.

[0015] This invention not only solves the technical challenges of comprehensive utilization of lithium resources, but also meets the domestic demand for ultra-pure cesium source materials for high-performance perovskite photovoltaic devices, providing a reliable raw material guarantee for the industrialization of next-generation high-efficiency, long-life photovoltaic products. Attached Figure Description

[0016] The accompanying drawings illustrate exemplary embodiments of the present application and, together with the description thereof, serve to explain the principles of the present application. These drawings are included to provide a further understanding of the present application and are incorporated in and constitute a part of this specification.

[0017] Figure 1 The flowchart of the method for recovering cesium sulfate and purifying it to prepare high-purity cesium iodide from lithium ore post-lithium extraction liquid provided by an embodiment of the present invention is shown.

[0018] Figure 2 XRD pattern of cesium iodide prepared in Example 1.

[0019] Figure 3 XRD pattern of cesium iodide prepared in Comparative Example 3.

[0020] Figure 4 Current-voltage curves of cesium iodide prepared in Example 1 in single-junction perovskite solar cells.

[0021] Figure 5 Current-voltage curves of cesium iodide prepared in Example 1 in inorganic CsPbI3 perovskite solar cells.

[0022] Figure 6 Comparison of photoelectric performance of cesium iodide prepared in Example 1 and Comparative Example 3 in single-junction perovskite solar cells. Detailed Implementation

[0023] Embodiments of this application will now be described in more detail with reference to the accompanying drawings. While some embodiments of this application are shown in the drawings, it should be understood that this application can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this application. It should be understood that the drawings and embodiments of this application are for illustrative purposes only and are not intended to limit the scope of protection of this application.

[0024] It should be noted that, where there is no conflict, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] The names of the messages or information exchanged between multiple devices in the embodiments of this application are for illustrative purposes only and are not intended to limit the scope of these messages or information.

[0026] Reference Figure 1 As shown, this embodiment of the invention provides a method for recovering cesium sulfate from lithium extraction liquid from lithium ore and purifying it to prepare high-purity cesium iodide, comprising the following steps: S1, after lithium extraction from lithium ore, the alkali is adjusted, and multi-stage countercurrent extraction is performed using an extractant and a diluent to selectively separate cesium ions and obtain a cesium-loaded organic phase; S2, the cesium-supported organic phase is washed with hydroiodic acid solution to remove co-extracted K. + Na + Impurity ions; S3, using hydroiodic acid solution as the back-extraction agent, yields a cesium-rich back-extraction solution (Cs). + Concentration ≥80g / L); S4, the cesium-rich back-extraction solution is de-oiled by passing it through a macroporous adsorption resin; S5, after oil removal, the solution is concentrated by rotary evaporation once and then frozen and crystallized twice before being filtered to obtain solid CsI; S6, CsI solid is washed with an anti-solvent to remove free iodine; S7. The washed CsI was calcined at 550~650℃ for 1 hour under a certain atmosphere to obtain high-purity cesium iodide powder.

[0027] As a further improvement, the method further includes: S8. The above-mentioned high-purity cesium iodide was applied to the preparation of perovskite solar cells, and its photoelectric performance was tested.

[0028] In step S1, the lithium extraction solution from the lithium ore contains cesium sulfate. The alkali adjustment involves adjusting the pH of the lithium extraction solution to approximately 13.3-14.5. Preferably, in one embodiment, the pH of the lithium extraction solution is adjusted to approximately 14.

[0029] As a further improvement, the extractant may be 4-tert-butyl-2-(α-methylbenzyl)phenol (t-BAMBP), and the diluent may be one or more of sulfonated kerosene, diethylbenzene, and liquid paraffin. In one embodiment, the extractant is used to dilute t-BAMBP with diethylbenzene, and the concentration of the extractant is 0.4~0.6 mol / L of t-BAMBP.

[0030] As a further improvement, in several embodiments, the O / A ratio for multi-stage countercurrent extraction is 1.8 to 2.2:1, and more preferably, the O / A ratio is 2:1, which achieves selective separation of cesium ions with extraction rates of 98.70%, 10.42%, 0.03%, and 0.58% for cesium, rubidium, sodium, and potassium, respectively. It can be understood that the selective separation of cesium ions can be maximized through the above-mentioned control of the extractant, diluent, and O / A ratio.

[0031] In step S2, preferably, the cesium-supported organic phase is washed with a 0.010–0.005 mol / L hydroiodic acid solution. In one embodiment, the cesium-supported organic phase is washed with a 0.008 mol / L hydroiodic acid solution to remove co-extracted K+. + Na + Impurity ions are added to improve the selectivity of cesium. The washing rates of cesium, rubidium, sodium, and potassium are 18.23%, >99.50%, >99.50%, and >99.50%, respectively.

[0032] In step S3, preferably, the cesium-loaded organic phase is washed using a 0.90-0.95 mol / L hydrogen iodide solution and subjected to a three-stage countercurrent back-extraction. The washed cesium-loaded organic phase is mixed with the hydrogen iodide solution at a volume ratio of 10-20:1, and after phase separation and clarification, a cesium-rich solution (Cs) is obtained. +(Concentration ≥80 g / L), the resulting empty organic phase is returned to the cesium extraction section for use. In one embodiment, the washed cesium-loaded organic phase is subjected to three-stage countercurrent back-extraction using a 0.91 mol / L hydrogen iodide solution. The washed cesium-loaded organic phase is then mixed with the hydrogen iodide solution at a volume ratio of 15:1. After phase separation and clarification, a cesium-rich solution (Cs) is obtained. + (Concentration ≥ 80 g / L), the resulting empty organic phase is returned to the cesium extraction section for use, and the Cs back-extraction rate is about 99%.

[0033] Preferably, in step S4, the back-extraction solution is treated with macroporous adsorption resin (such as HEPREM resin) to remove residual extractant, so that TOC ≤ 5 ppm and COD ≤ 10 ppm, thus avoiding contamination in subsequent processes.

[0034] Preferably, in step S5, the solution is concentrated by rotary evaporation (80°C) once to reduce the oil-removed solution to 10% of its original concentration; and then frozen and crystallized (0°C) a second time to further concentrate and precipitate CsI crystals. The mother liquor is returned to the extraction process to achieve efficient enrichment of cesium (recovery rate ≥90%).

[0035] Preferably, in step S6, the unreacted free iodine is dissolved by washing with an antisolvent (one or more of ethanol, isopropanol, acetone, benzene or carbon tetrachloride) (I2 removal rate ≥95%).

[0036] Preferably, in step S7, the washed cesium iodide is calcined at 600°C for 1 hour in air to completely remove residual iodine and organic impurities, thereby obtaining high-purity cesium iodide powder with a purity of >99.995%.

[0037] Example 1: In this embodiment, a lithium mica lithium precipitation mother liquor was used as raw material, and its main components are shown in Table 1.

[0038] Table 1. Element content of lithium-containing mother liquor from a certain lepidolite deposit / g / L

[0039] *Unit is mg / L Cesium extraction of lithium precipitate mother liquor: The pH of the lithium ore post-lithium extraction liquor (containing cesium sulfate, rubidium sulfate, etc.) was adjusted to 14.0. 4-tert-butyl-2-(α-methylbenzyl)phenol (t-BAMBP) was used as the extractant and diethylbenzene as the diluent (0.4~0.6 mol / L t-BAMBP). Multi-stage countercurrent extraction was carried out under an O / A ratio of 2:1.

[0040] Washing of the cesium-supported organic phase: The cesium-supported organic phase was washed with 0.008 mol / L hydroiodic acid solution.

[0041] Cesium-loaded organic phase back-extraction: The washed cesium-loaded organic phase was subjected to three-stage countercurrent back-extraction using 0.91 mol / L hydrogen iodide solution. The washed cesium-loaded organic phase was then mixed with hydrogen iodide solution at a volume ratio of 15:1. After phase separation and clarification, a cesium-rich solution (Cs) was obtained. + (Concentration ≥ 80 g / L), the resulting empty organic phase is returned to the cesium extraction section for use, and the Cs back-extraction rate is about 99%.

[0042] Resin degreasing: The back-extraction solution is degreased by passing it through a macroporous adsorption resin (such as HEPREM resin) to remove residual extractant, so that TOC ≤ 5 ppm and COD ≤ 10 ppm, thus avoiding contamination in subsequent processes.

[0043] Gradient concentration: First, rotary evaporation concentration (80℃) reduces the oil-removed solution to 10% of its original concentration; second, freeze-crystallization (0℃) further concentrates and precipitates CsI crystals, and the mother liquor is returned to the extraction process to achieve efficient enrichment of cesium (recovery rate ≥90%).

[0044] Antisolvent removal: Washing with antisolvent ethanol to dissolve unreacted free iodine (I2 removal rate ≥95%).

[0045] Calcination and drying: The washed cesium iodide was calcined at 600°C for 1 hour in air to completely remove residual iodine and organic impurities, yielding high-purity cesium iodide powder with a purity >99.995%. The XRD pattern of the obtained high-purity cesium iodide is shown below. Figure 2 As shown, the phase composition is consistent with that of standard card PDF#06-0311.

[0046] Comparative Example 1: The difference from Example 1 is that the back-extraction solution was not treated with macroporous adsorption resin for oil removal. Table 2 shows the TOC and COD content of the CsI back-extraction solution before and after oil removal treatment with macroporous adsorption resin. Before oil removal, the TOC was 6.2 ppm and the COD was 22 ppm; after oil removal, the TOC was 3.1 ppm and the COD was 8 ppm. This indicates that adding an oil removal treatment to the back-extraction solution can effectively remove residual extractant, resulting in TOC ≤ 5 ppm and COD ≤ 10 ppm, thus avoiding contamination in subsequent processes.

[0047] Table 2 shows the TOC and COD contents (mg / L) of the CsI back-extraction solution before and after oil removal treatment by macroporous adsorption resin.

[0048] Comparative Example 2: The difference from Example 1 is that the back-extraction solution was not concentrated by freeze crystallization. The cesium iodine elemental composition of the CsI product was tested and is shown in Table 3. The K and Na contents of the CsI product obtained without freeze crystallization of the back-extraction solution were higher than those of the CsI product obtained by freeze crystallization (with the freeze-drying temperature controlled at 4°C).

[0049] Table 3 shows the elemental content (%) of the back-extraction solution with and without freeze crystallization and concentration.

[0050] Comparative Example 3: The difference from Example 1 is that the back-extraction solution was not purified using an anti-solvent. The sample turned pale yellow after calcination. The elemental ratios of the CsI products were tested, and the iodine / cesium ratio of the product without anti-solvent purification was 1.083:1, which is greater than that of the CsI product with anti-solvent purification, as shown in Table 4. Further testing of the phase composition of the CsI product without anti-solvent purification showed that the peak intensity ratios were inconsistent with those of the standard card PDF#06-0311. Figure 3 As shown.

[0051] Table 4 shows the iodine and cesium content of the back-extraction solution with and without antisolvent treatment.

[0052] Application Example 2: This embodiment provides a method for using cesium iodide (Example 1) prepared by recycling and purifying cesium sulfate from lithium ore after lithium extraction for use in perovskite batteries, as detailed below: (1) Substrate pretreatment: The patterned ITO glass substrate was deeply cleaned by a multi-step ultrasonic cleaning process: neutral detergent, deionized water, acetone and isopropanol were used in sequence for ultrasonic treatment for 15 minutes each, and finally dried with high-purity nitrogen.

[0053] (2) Hole transport layer preparation: In an air environment, a pre-synthesized nickel oxide nanoparticle dispersion (concentration 20 mg / mL) was spin-coated onto the ITO surface at a speed of 2000 rpm for 30 seconds, and then annealed on a hot plate at 200℃ for 10 minutes to form a dense nickel oxide hole transport layer.

[0054] (3) Preparation of self-assembled molecular layer: In a nitrogen glove box (O2<0.1 ppm, H2O<0.1 ppm), the MeO-2PACZ self-assembled molecular solution (0.5 mg / mL ethanol solution) was spin-coated onto the nickel oxide layer surface at 3000 rpm for 30 seconds, and then annealed at 100℃ for 10 minutes.

[0055] (4) Preparation of perovskite active layer: A mixed cation perovskite precursor solution (Cs) was prepared using commercially available cesium iodide and cesium iodide prepared in Example 1, respectively. 0.05 Rb 0.01 FA 0.92 MA 0.02 Pb(I 0.95 Br 0.053). MABr, CsI, RbI, PbBr2, FAI, and PbI2 were dissolved in a stoichiometric ratio in a DMF:DMSO (4:1 v / v) mixed solvent to obtain a 1.4 M clear solution. A two-step spin-coating process was used: first, spin-coating was performed at 3000 rpm for 40 seconds; then, 120 μL of chlorobenzene was added dropwise in the last 35 seconds as an anti-solvent to induce rapid crystallization. The solution was then immediately transferred to a hot plate at 100°C for annealing for 10 minutes to obtain a perovskite thin film.

[0056] (5) Preparation of electron transport layer: First, spin-coat PEAI passivation layer (0.2 mg / mL isopropanol solution, 3000 rpm, 30 seconds) and anneal at 100℃ for 5 minutes; then spin-coat PCBM electron transport layer (20 mg / mL chlorobenzene solution, 2000 rpm, 30 seconds) and anneal at 100℃ for 4 minutes; finally deposit BCP buffer layer (0.5 mg / mL isopropanol solution, 5000 rpm, 30 seconds) and anneal at 100℃ for 1 minute.

[0057] (6) Metal electrode preparation: A high-vacuum thermal evaporation system (pressure <5×10⁻) was used. 4 A 100 nm silver electrode was deposited on the device surface by evaporation at a rate controlled between 0.2 and 0.3 nm / s, ultimately yielding a complete device with an effective area of ​​0.04 cm².

[0058] The performance of the single-junction perovskite solar cell device fabricated in Example 2 was tested, and the results are as follows: Figure 4 As shown in the figure, the device has a forward scanning photoelectric conversion efficiency of 22.2%, an open-circuit voltage of 1.118 V, and a short-circuit current density of 23.8 mA / cm². 2 The fill factor is 83.9%; the reverse scanning photoelectric conversion efficiency is 22.3%; the open-circuit voltage is 1.120 V; and the short-circuit current density is 23.8 mA / cm². 2 The fill factor is 84.5%. The efficiency difference between forward and reverse scans is 0.1%, with a small hysteresis effect (hysteresis index = 0.0045 << 0.05), significantly better than conventional perovskite devices (hysteresis index is usually > 0.1), indicating excellent interfacial charge transport balance, which can be attributed to the low defect density of the perovskite film. Both forward and reverse scan FFs are > 83%, reflecting low series resistance and high parallel resistance. Furthermore, the device's forward and reverse scan efficiency... J sc Completely consistent, with excellent current output stability.

[0059] Application Example 3 This embodiment provides a method for using cesium iodide prepared by recycling and purifying cesium sulfate from lithium ore post-lithium extraction liquid for inorganic CsPbI3 perovskite batteries, as detailed below: (1) Substrate pretreatment: Take the laser-etched FTO conductive glass (sheet resistance 8.5 Ω / sq), and ultrasonically clean it in deionized water, ethanol, acetone and isopropanol for 20 minutes in sequence; after blowing it dry with high-purity nitrogen, dry it in an 80℃ oven for 8 hours; before use, perform ultraviolet ozone treatment for 30 minutes, with a power density ≥15 mW / cm².

[0060] (2) Preparation of electron transport layer: 0.125 M titanium isopropoxide (TTIP) sol precursor was spin-coated onto the FTO surface at 3000 rpm for 30 seconds; it was then sintered in a muffle furnace at 500℃ for 1 hour at a heating rate of 5℃ / min and naturally cooled to room temperature; an aqueous solution of 10 mM CsBr and 0.1 wt% 18-crown-6 ether (18C6) was spin-coated onto the TiO2 substrate at 4000 rpm and heat-treated at 100℃ for 10 minutes.

[0061] (3) Preparation of CsPbI3 perovskite active layer: The substrate was quickly transferred to a nitrogen glove box (H2O<0.1 ppm, O2<0.1 ppm); a two-step spin coating method was adopted: the first step was to spin coat at 1500 rpm for 10 seconds to accelerate the uniform coating; the second step was to spin coat at 4000 rpm for 30 seconds, and 150 μL of chlorobenzene was added as an anti-solvent 5 seconds before the end of the spin coating; the substrate was first heat-treated at 70℃ for 3 minutes in the glove box, and then transferred to a humidity-controlled environment (20±2% RH) for annealing at 190℃ for 10 minutes.

[0062] (5) Hole transport layer preparation: Spiro-OMeTAD solution (containing 72.3 mg Spiro-OMeTAD, 28.8 μL 4-tert-butylpyridine and 17.5 μL Li-TFSI / acetonitrile solution) was spin-coated at 3000 rpm for 25 seconds; then heat-treated at 60℃ for 5 minutes to form a hole transport layer.

[0063] (6) Metal electrode preparation: A high-vacuum thermal evaporation system (pressure <5×10⁻) was used. 4 A 100 nm gold electrode is deposited on the device surface using a mask, with the effective area of ​​the mask limited to 0.09 cm².

[0064] The performance of the inorganic CsPbI3 perovskite solar cell device prepared in Example 3 was tested, and the results are as follows: Figure 5 As shown in the figure, the device has a forward scanning photoelectric conversion efficiency of 19.8%, an open-circuit voltage of 1.113 V, and a short-circuit current density of 22.5 mA / cm². 2 The fill factor is 79.5%; the reverse scanning photoelectric conversion efficiency is 20.1%; the open-circuit voltage is 1.115 V; and the short-circuit current density is 22.2 mA / cm². 2The fill factor is 81.7%. The device exhibits good initial efficiency (stable at around 20%) and small hysteresis effect (hysteresis index <0.02), indicating that the cesium iodide provided by this invention helps to realize the fabrication of high-efficiency inorganic CsPbI3 perovskite solar cells.

[0065] Application Example 4 The CsI samples from Example 1 and Comparative Example 3 were used to fabricate single-junction perovskite solar cells, and the photoelectric properties of the perovskite solar cells were obtained as follows: Figure 6 As shown. The device prepared in Example 1 has an average photoelectric conversion efficiency of 21.4%, an open-circuit voltage of 1.130 V, and a short-circuit current density of 23.2 mA / cm². 2 The fill factor was 82.0%; the device prepared in Comparative Example 3 had an average photoelectric conversion efficiency of 20.9%, an open-circuit voltage of 1.123 V, and a short-circuit current density of 23.0 mA / cm². 2 The fill factor was 81.9%. The Voc of the device in Example 1 increased by 7 mV (+0.62%), indicating that higher purity and purer phase CsI is beneficial to reducing the bulk defect density of the perovskite film; while the increase in short-circuit current density (Jsc) (0.2 mA / cm²) indicates that CsI products with near stoichiometry are beneficial to the formation of a better perovskite crystal structure, ultimately improving the cell efficiency of the perovskite solar cell.

[0066] Those skilled in the art should understand that the above embodiments are merely for illustrative purposes and are not intended to limit the scope of this application. Those skilled in the art can make other changes or modifications based on the above disclosure, and these changes or modifications still fall within the scope of this application.

Claims

1. A method for preparing high-purity cesium iodide, characterized in that: Includes the following steps: S1, after lithium extraction from lithium ore, the alkali is adjusted, and multi-stage countercurrent extraction is performed using an extractant and a diluent to selectively separate cesium ions and obtain a cesium-loaded organic phase; S2, the cesium-supported organic phase is washed with hydroiodic acid solution to remove co-extracted K. + Na + Impurity ions; S3, using hydroiodic acid solution as the back-extraction agent, back-extraction is performed to obtain a cesium-rich back-extraction solution; S4, the cesium-rich back-extraction solution is de-oiled by passing it through a macroporous adsorption resin; S5, after oil removal, the solution is concentrated by rotary evaporation once and then frozen and crystallized twice before being filtered to obtain solid CsI; S6, CsI solid is washed with an anti-solvent to remove free iodine; S7. The washed CsI is calcined at 550~650℃ under a certain atmosphere to obtain high-purity cesium iodide powder.

2. The method as described in claim 1, characterized in that: In step S1, the alkali adjustment is to adjust the pH value of the lithium ore extraction solution to 13.3~14.

5.

3. The method as described in claim 1, characterized in that: In step S1, the extractant is 4-tert-butyl-2-(α-methylbenzyl)phenol (t-BAMBP), and the diluent is one or more of sulfonated kerosene, diethylbenzene, and liquid paraffin.

4. The method as described in claim 3, characterized in that: The O / A ratio for multi-stage countercurrent extraction is 1.8~2.2:

1.

5. The method as described in claim 1, characterized in that: In step S2, the cesium-supported organic phase is washed with a 0.010~0.005 mol / L hydroiodic acid solution.

6. The method as described in claim 1, characterized in that: In step S3, the cesium-carrying organic phase is washed with a 0.90~0.95mol / L hydrogen iodide solution and subjected to three-stage countercurrent back-extraction. The washed cesium-carrying organic phase and the hydrogen iodide solution are mixed at a volume ratio of 10~20:

1. After phase separation and clarification, a cesium-rich solution is obtained.

7. The method as described in claim 1, characterized in that: In step S6, unreacted free iodine is dissolved by washing with one or more antisolvents selected from ethanol, isopropanol, acetone, benzene, or carbon tetrachloride.

8. A high-purity cesium iodide, characterized in that: The high-purity cesium iodide is obtained by the method described in any one of claims 1-7.

9. An application of the high-purity cesium iodide as described in claim 8 in perovskite solar cells.

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