A method for preparing stannous iodide

Abstract

The application belongs to the field of new energy materials, and provides a preparation method of stannous iodide, which comprises the following steps: adding hydriodic acid into ultrapure water to configure a solution A; adding a tin source into pure water, and then adding an antioxidant to form a solution B; adding the solution A into the solution B, heating and reacting, and then adding a reaction catalyst, stirring, and obtaining an orange-red solid; separating the orange-red solid from a liquid, washing, and vacuum drying to obtain a crude stannous iodide; performing a first heating process on the crude stannous iodide to separate the stannous iodide from oxidized impurities; and then performing a second heating process to obtain stannous iodide for perovskite batteries through high-temperature purification; wherein the tin source contains divalent tin ions. The preparation method has mild reaction conditions, simple raw material acquisition and preservation, high reaction efficiency, and the prepared finished product has high quality and high purity and is not easy to be oxidized, and is used in narrow-bandgap perovskite solar cells and laminated solar cells, and the photoelectric conversion efficiency is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials, specifically relating to a method for preparing stannous iodide. Background Technology

[0002] Metal halide perovskite materials, due to their adjustable bandgap and solution-processable fabrication capabilities, can achieve photoelectric conversion efficiencies exceeding 30% by fabricating tandem perovskite solar cells with two, three, or even multiple segments, making them a key material for future photovoltaic power generation. A tandem perovskite solar cell consists of at least two parts: a narrow-bandgap perovskite solar cell and a wide-bandgap perovskite solar cell. Narrow-bandgap perovskite materials are typically composed of formamidinium lead tin iodide (FA(PbSn)I3), with tin typically comprising over 70% of the material. Wide-bandgap perovskite materials are typically composed of formamidinium lead halide (FAPbX3). Narrow-bandgap perovskite materials absorb more photon energy and contribute more to the photovoltaic module current. The most crucial factor determining the performance of narrow-bandgap perovskite materials is the quality of the raw material, tin iodide.

[0003] Since tin iodide is very easily oxidized and transformed into tetravalent tin iodide, and tin iodide cannot form a perovskite structure with organic cation halides to achieve photoelectric conversion, how to prepare stable, non-oxidized tin iodide that does not contain tetravalent tin has become the key to restricting the development of tandem perovskite solar cells.

[0004] Currently, the main methods for preparing stannous iodide are either by reacting tin powder and elemental iodine in hydrochloric acid solution, or by sealing tin powder and tin iodide in a closed quartz tube to produce stannous iodide. Both methods have certain problems: (1) It is difficult to obtain and preserve the raw materials. Elemental iodine is highly volatile, and hydrochloric acid, as an extremely dangerous strong acid, will endanger production safety and cause environmental pollution; (2) The reaction between elemental iodine and tin powder is extremely slow and requires ultra-high temperature stirring. The process is accompanied by a large amount of hydrochloric acid volatilization, which will lead to a decrease in the acidity of the system, making stannous iodide more likely to undergo hydrolysis and oxidation in water; (3) The method of sealing tin powder and tin iodide in a quartz tube poses a risk of explosion of the sealed container, and the degree of reaction cannot be controlled. Elemental tin and tetravalent tin are likely to remain in the final product.

[0005] Therefore, there is an urgent need to develop a method for preparing stannous iodide that is mild in reaction conditions, simple in obtaining and storing raw materials, and highly efficient in reaction. At the same time, the prepared product should be of high quality, high purity, and not easily oxidized, and could be used to prepare high-efficiency narrow bandgap perovskite solar cells and tandem solar cells. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for preparing stannous iodide. This method features mild reaction conditions, simple raw material acquisition and storage, and is a highly efficient method for preparing stannous iodide. Furthermore, the prepared product is of high quality, high purity, and is not easily oxidized. The stannous iodide prepared by this invention can be used in narrow bandgap perovskite solar cells and tandem solar cells, significantly improving photoelectric conversion efficiency.

[0007] The purpose of this invention is to provide a method for preparing stannous iodide, comprising the following steps:

[0008] (1) Add hydroiodic acid to ultrapure water to prepare solution A;

[0009] (2) Add the tin source to pure water, then add an antioxidant to form solution B;

[0010] (3) After filtering solution B, add it to the reaction apparatus and continuously pass in inert gas. After the inert gas removes oxygen for a certain period of time, add solution A from step (1) to solution B, heat the reaction, add the reaction catalyst, stir, and obtain an orange-red solid.

[0011] (4) Separate the orange-red solid from the liquid in step (3), wash, and vacuum dry to obtain crude stannous iodide;

[0012] (5) The crude stannous iodide is subjected to a first heating process to separate the stannous iodide from the oxidized impurities; then a second heating process is carried out for high-temperature purification to obtain stannous iodide for perovskite batteries.

[0013] In step (2), the tin source contains divalent tin ions.

[0014] The preparation method of this invention uses stable and readily available raw materials; the reaction is a relatively rapid precipitation reaction with mild reaction conditions, greatly shortening the production cycle; adding an antioxidant to the tin source solution can inhibit the oxidation of divalent tin throughout the entire feeding and reaction process; adding a reaction catalyst promotes the formation of branched crystals of stannous iodide, accelerates the reaction progress, maintains the stability of the stannous iodide crystal structure, further inhibits the oxidation of stannous iodide in various environments, and shortens the reaction time; the high-temperature purification process utilizes the phase transition phenomenon of stannous iodide from solid to gas to remove trace impurities. Under the combined effect of the above, the preparation method of this invention produces stannous iodide with high purity, stability, and resistance to oxidation, which significantly improves the photoelectric conversion efficiency of perovskite solar cells.

[0015] Furthermore, the solution A obtained in step (1) has an HI concentration of 10~35wt%.

[0016] Further, the tin source in step (2) includes at least one of stannous chloride, stannous chloride dihydrate, and stannous fluoride. Preferably, the amount of tin source used is 80-98% of the amount of HI in step (1). Excess hydroiodic acid can inhibit the hydrolysis and oxidation of divalent tin during the reaction.

[0017] Furthermore, in step (2), the antioxidant includes at least one of tert-butylhydroquinone and butylated hydroxytoluene. This antioxidant can be completely removed during subsequent heating purification with stannous iodide. Preferably, the amount of antioxidant used is 3-8% of the amount of HI in step (1).

[0018] Furthermore, in step (3), the inert gas deoxygenation time is 10-120 minutes. The heating temperature is 65-85℃, and the heating reaction time is 20-60 minutes.

[0019] Furthermore, in step (3), the reaction catalyst includes at least one of elemental tin and elemental iron. This catalyst can be completely removed during subsequent heating purification of stannous iodide. Preferably, the amount of reaction catalyst used is 1-4% of the amount of HI in step (1).

[0020] Furthermore, in step (4), the vacuum drying temperature is 70~100℃.

[0021] Further, in step (5), a three-zone tubular furnace is used for heating treatment. In the first heating process, the first zone is heated to 150~170℃, the second zone is heated to 150~170℃, and the third zone is heated to 150~170℃ for a heating time of 180~320min. In the second heating process, the first zone is heated to 320~360℃, the second zone is heated to 170~190℃, and the third zone is cooled and kept at 40~60℃ for a heating time of 180~320min.

[0022] The three-zone tube furnace used in this invention is divided into three zones, which are heated simultaneously. Tin iodide is placed in the first zone, where impurities oxidized during the first heating process volatilize at around 150°C. During the second heating process, the tin iodide volatilizes and deposits in the second zone, while the less volatile impurities remain in the first zone, thus achieving separation.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The preparation method of this invention features mild reaction conditions, stable raw materials, and simple acquisition and storage. It is a highly efficient method for preparing stannous iodide, significantly shortening the reaction time. This preparation method is convenient for industrialization, exhibits extreme stability, and produces high-quality, high-purity products that are not easily oxidized, meeting the requirements for use as precursor materials in perovskite solar cells. When used in perovskite solar cells and tandem solar cells, it significantly improves the photoelectric conversion efficiency of perovskite solar cells. Attached Figure Description

[0025] Figure 1 The images show the appearance and SEM microstructure of tin iodide obtained in Example 1.

[0026] Figure 2 The XRD pattern of stannous iodide obtained in Example 1;

[0027] Figure 3 The XRD pattern of the tin iodide product obtained in Comparative Example 2 is shown. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] The purpose of this invention is to provide a method for preparing stannous iodide that can be easily industrialized, resulting in a method with high quality, high purity, and extreme stability, which can be used for the preparation of high-efficiency tandem perovskite solar cells.

[0030] The present invention adopts the following technical solution:

[0031] Stannous iodide is synthesized through the following steps:

[0032] Step (1): Add hydroiodic acid to ultrapure water, stir, and dilute to a certain concentration to prepare solution A;

[0033] Step (2): Add a certain amount of tin source to pure water, then add a certain amount of antioxidant, and stir to form solution B;

[0034] Step (3): After filtering solution B, put it into a three-necked flask and continuously introduce nitrogen into the three-necked flask; after removing oxygen with nitrogen for a certain period of time, add solution A from step (1) into solution B, heat the reaction for a certain period of time, add a certain amount of reaction catalyst, and continue stirring to obtain an orange-red solid.

[0035] Step (4): Separate the orange-red solid from the liquid in step (3), wash with ethanol three times, and then vacuum dry to obtain crude stannous iodide;

[0036] Step (5): Place the crude tin iodide into the first temperature zone of a three-temperature zone tube furnace for the first heating process to separate the tin iodide from the oxidized impurities; after the first heating process is completed, perform the second heating process to obtain high-purity tin iodide for perovskite batteries in the second temperature zone.

[0037] Preferably, the concentration mentioned in step (1) is 10~35% (mass fraction).

[0038] Preferably, the tin source in step (2) is one of stannous chloride, stannous chloride dihydrate, and stannous fluoride, and the certain amount of tin source is 80-98% of the amount of hydroiodic acid.

[0039] Preferably, the antioxidant mentioned in step (2) is one of tert-butylhydroquinone and butylated hydroxytoluene, and the certain amount of antioxidant is 3 to 8% of the amount of hydroiodic acid.

[0040] Preferably, the nitrogen deoxygenation time in step (3) is 10 to 120 minutes, and the heating reaction time is 20 to 60 minutes.

[0041] Preferably, the reaction catalyst in step (3) is one of elemental tin or elemental iron, and the certain amount of reaction catalyst is 1 to 4% of the amount of hydroiodic acid.

[0042] Preferably, the vacuum drying temperature in step (4) is 70~100℃.

[0043] Preferably, in step (5), the first heating process has a first temperature zone of 150-170°C, a second temperature zone of 150-170°C, a third temperature zone of 150-170°C, and a heating time of 180-320 minutes; the second heating process has a first temperature zone of 320-360°C, a second temperature zone of 170-190°C, a third temperature zone of 40-60°C, and a heating time of 180-320 minutes.

[0044] The advantages of this invention compared to existing stannous iodide synthesis techniques are as follows:

[0045] First, common methods for preparing stannous iodide typically require elemental iodine and hydrochloric acid. These two raw materials are difficult to preserve and pose significant hazards. For example, elemental iodine is highly volatile at room temperature, harming human health and easily damaging equipment; hydrochloric acid is a hazardous chemical and a precursor to toxic substances, making it unsuitable for large-scale stannous iodide production. This invention uses stable and readily available low-purity stannous chloride dihydrate, stannous fluoride, and hydroiodic acid as raw materials, solving the problem of large-scale production caused by the hazardous and unstable nature of the raw materials in the stannous iodide preparation process. Second, the reaction of stannous chloride or stannous fluoride with hydroiodic acid is a relatively rapid precipitation reaction, unlike the relatively slow oxidation reaction of elemental iodine and tin, which generally requires tens of hours and sustained high temperatures. The method used in this invention significantly shortens the production cycle and avoids the problem of stoichiometric deviations caused by incomplete reactions between the elements. Third: This invention reduces tetravalent tin ions to divalent tin ions by adding specific antioxidants during the raw material preparation stage without introducing other impurities, thus solving the problem of easy hydrolysis and oxidation of tin sources after dissolving in water. Simultaneously, the addition of a certain amount of reaction catalyst during the reaction stage promotes the growth and crystallization of stannous iodide, further shortening the reaction time and enhancing the air stability of the finished stannous iodide product. Fourth: This invention purifies stannous iodide in an open three-zone tube furnace, obtaining stannous iodide with a purity similar to that found in traditional quartz tubes, without the risks of quartz tube explosions or uncontrolled iodine-tin ratios. Furthermore, it completely removes the antioxidants and reaction catalysts added in previous steps, maintaining the high purity of the material.

[0046] The technical principles involved in this invention are as follows: (1) Stannous iodide is produced by reacting a stable and relatively safe tin-containing compound (stannous chloride or stannous fluoride) in the air with hydroiodic acid using a precipitation reaction. (2) In the reaction formula, hydroiodic acid is in excess, which can inhibit the hydrolysis and oxidation of divalent tin during the reaction process. The antioxidant added to the tin source solution can inhibit the oxidation of divalent tin cations throughout the entire formulation and reaction process. (3) A reaction catalyst is added during the reaction process, mainly to promote the formation of branched crystals of stannous iodide, accelerate the reaction progress, maintain the stability of the stannous iodide crystal structure, and further inhibit the oxidation of stannous iodide in various environments. (4) In the final high-temperature purification process, the phase transition phenomenon of stannous iodide from solid to gas at 300~340℃ is used to remove trace impurities in stannous iodide, and finally high-purity, stable, and non-oxidized stannous iodide is obtained, which can be used to prepare high-efficiency tandem perovskite solar cells.

[0047] Example 1

[0048] 1. Pass 600 mL of 57wt% hydroiodic acid into 1280 mL of ultrapure water, stir, and dilute to a certain concentration to prepare solution A.

[0049] 2. Add 430g of stannous chloride dihydrate to 1000 mL of pure water, then add 17g of tert-butylhydroquinone, and stir to form solution B.

[0050] 3. After filtering solution B, put it into a three-necked flask and then purge the three-necked flask with nitrogen for 10 minutes. After the nitrogen has removed oxygen for a certain period of time, add solution A from step 1 to solution B, and an orange solid will be obtained. After heating the reaction at 80°C for 20 minutes, add 5g of tin powder and continue heating and stirring. After 120 minutes, an orange-red solid will be obtained.

[0051] 4. Separate the orange-red solid from the liquid in step 3, wash with ethanol three times, and dry under vacuum at 70°C for 12 hours to obtain a total of 658g of crude stannous iodide.

[0052] 5. The crude stannous iodide is placed in the first temperature zone of a three-zone tube furnace for the first heating process. The first temperature zone is 160℃, the second temperature zone is 155℃, and the third temperature zone is 150℃. After heating for 180 minutes, the material on the tube walls of the second and third temperature zones is scraped off to separate the stannous iodide from the oxidized impurities. After the first heating process, a second heating process is performed. The first temperature zone is 340℃, the second temperature zone is 180℃, and the third temperature zone is 50℃. After heating for 300 minutes, all the stannous iodide will be deposited in the second temperature zone, yielding 605g of high-purity stannous iodide for perovskite batteries.

[0053] ICP testing showed that the product prepared in Example 1 had a purity of 99.997%. The XRD pattern of stannous iodide obtained in Example 1 is shown below. Figure 2 As shown in the XRD pattern, no tetravalent tin iodide was generated in the product, indicating that the tin iodide of the present invention has good stability and is not easily oxidized, thus meeting the requirements for a perovskite solar cell precursor material.

[0054] Comparative Example 1

[0055] The difference between Comparative Example 1 and Example 1 is that no reaction catalyst is added to the components.

[0056] 1. Pass 600 mL of 57% hydroiodic acid into 1280 mL of ultrapure water, stir, and dilute to a certain concentration to prepare solution A;

[0057] 2. Add 430g of stannous chloride dihydrate to 1000mL of pure water, then add 17g of tert-butylhydroquinone, and stir at room temperature for 30 minutes to form solution B;

[0058] 3. After filtering solution B, put it into a three-necked flask and then purge the three-necked flask with nitrogen for 10 minutes. After the nitrogen has deoxygenated for a certain period of time, add solution A from step 1 to solution B. An orange solid will be produced in the solution. After stirring at 80°C for 620 minutes, the color of the orange solid will change to orange-red.

[0059] 4. Separate the orange-red solid from the liquid in step 3, wash with ethanol three times, and dry under vacuum at 70°C for 12 hours to obtain a total of 640g of crude stannous iodide.

[0060] 5. Place the crude stannous iodide into the first temperature zone of a three-zone tube furnace for the first heating process. The temperature of the first temperature zone is 160℃, the temperature of the second temperature zone is 155℃, and the temperature of the third temperature zone is 150℃. After heating for 180 minutes, the stannous iodide and the oxidized impurities are separated. After the first heating process is completed, the second heating process is carried out. The temperature of the first temperature zone is 340℃, the temperature of the second temperature zone is 180℃, and the temperature of the third temperature zone is 50℃. After heating for 300 minutes, a total of 585g of stannous iodide is obtained in the second temperature zone.

[0061] In the synthesis process of Comparative Example 1, a reaction time of up to 620 minutes was required to produce an orange-red solid (stannous iodide), indicating that the reaction catalyst added in Example 1 of this invention has the effect of promoting the reaction process.

[0062] Comparative Example 2

[0063] The difference between Comparative Example 2 and Example 1 is that no antioxidants are added to the components.

[0064] 1. Pass 600 mL of 57% hydroiodic acid into 1280 mL of ultrapure water, stir, and dilute to a certain concentration to prepare solution A;

[0065] 2. Add 430g of stannous chloride dihydrate to 1000mL of pure water and stir at room temperature for 30 minutes to form solution B;

[0066] 3. After filtering solution B, put it into a three-necked flask and then purge the three-necked flask with nitrogen for 10 minutes. After the nitrogen has deoxygenated for a certain period of time, add solution A from step 1 to solution B, and an orange solid will be obtained. After heating and reacting for 20 minutes, add 5g of tin powder, continue heating and stirring, and after 120 minutes, an orange-red solid will be obtained.

[0067] 4. Separate the orange solid from the liquid in step 3, and dry it under vacuum at 70°C for 12 hours to obtain a total of 690g of crude stannous iodide;

[0068] 5. Place the crude stannous iodide into the first temperature zone of a three-zone tube furnace for the first heating process. The first temperature zone is 160℃, the second temperature zone is 155℃, and the third temperature zone is 150℃. After heating for 180 minutes, the stannous iodide and the oxidized impurities are separated. After the first heating process is completed, the second heating process is carried out. The first temperature zone is 340℃, the second temperature zone is 180℃, and the third temperature zone is 50℃. After heating for 300 minutes, 505g of high-purity stannous iodide for perovskite batteries is obtained in the second temperature zone.

[0069] The final yield of stannous iodide in the second temperature zone was relatively low, mainly because stannous iodide was oxidized during the reaction, transforming into tin iodide, which then entered the third temperature zone, resulting in some separation. The XRD pattern of the stannous iodide product obtained in Comparative Example 2 is shown below. Figure 3 As shown in the XRD pattern, the product in Comparative Example 2 shows obvious tetravalent tin iodide production, indicating that tin iodide is easily oxidized during the synthesis of tin iodide, while antioxidants play a role in inhibiting oxidation.

[0070] Application examples

[0071] The performance of narrow bandgap perovskite solar cells prepared using the products of Example 1, Comparative Example 1, and Comparative Example 2 is shown in the table below.

[0072]

[0073] As can be seen from the data in the table, the narrow bandgap perovskite solar cell prepared from the product of Example 1 has an efficiency of 21.1%, which can meet the requirements of tandem perovskite photovoltaic modules.

[0074] The narrow bandgap perovskite solar cell prepared from the product of Comparative Example 1 has an efficiency of only 18.5%, which is about 3% lower than that of Example 1.

[0075] The narrow bandgap perovskite solar cell prepared from the product of Comparative Example 1 had an efficiency of only 14.4%, and the oxidation of divalent tin severely affected the efficiency of the perovskite solar cell.

[0076] In summary, the preparation method of this invention uses milder reaction conditions and more stable raw materials compared to existing technologies. The resulting stannous iodide has a purity of 99.997% as determined by ICP testing. The XRD pattern of the stannous iodide obtained in Example 1 shows that no tetravalent tin iodide is formed in the product. The stannous iodide prepared by this invention exhibits good stability and is not easily oxidized, meeting the requirements for a precursor material in perovskite solar cells. When used in perovskite solar cells, it significantly improves the photoelectric conversion efficiency of perovskite solar cells.

[0077] The above embodiments are for illustrative purposes only and are not intended to limit the invention. Those skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention. Therefore, all equivalent technical solutions should also fall within the scope of the invention and should be defined by the claims.

Claims

1. A method for preparing stannous iodide, characterized in that, Includes the following steps, (1) Add hydroiodic acid to ultrapure water to prepare solution A; (2) Add the tin source to pure water, then add an antioxidant to form solution B; (3) After filtering solution B, add it to the reaction apparatus, pass in inert gas, add solution A from step (1) to solution B, heat the reaction, add the reaction catalyst, stir, and obtain an orange-red solid; (4) Separate the orange-red solid from the liquid in step (3), wash, and vacuum dry to obtain crude stannous iodide; (5) The crude stannous iodide is subjected to a first heating process to separate the stannous iodide from the oxidized impurities; then a second heating process is carried out for high-temperature purification to obtain stannous iodide for perovskite batteries. In step (2), the tin source contains divalent tin ions.

2. The preparation method according to claim 1, characterized in that, The solution A obtained in step (1) has an HI concentration of 10~35wt%.

3. The preparation method according to claim 1, characterized in that, In step (2), the tin source includes at least one of stannous chloride, stannous chloride dihydrate, and stannous fluoride.

4. The preparation method according to claim 3, characterized in that, The amount of tin source used is 80-98% of the amount of HI substance.

5. The preparation method according to claim 1, characterized in that, In step (2), the antioxidant includes at least one of tert-butylhydroquinone and butylated hydroxytoluene.

6. The preparation method according to claim 1, characterized in that, In step (3), the reaction catalyst includes at least one of elemental tin and elemental iron.

7. The preparation method according to claim 1, characterized in that, In step (5), a three-zone tubular furnace is used for heating treatment. In the first heating process, the temperature of the first zone is 150~170℃, the temperature of the second zone is 150~170℃, the temperature of the third zone is 150~170℃, and the heating time is 180~320min. In the second heating process, the temperature of the first zone is 320~360℃, the temperature of the second zone is 170~190℃, the temperature of the third zone is 40~60℃, and the heating time is 180~320min.

8. The stannous iodide prepared by the preparation method according to any one of claims 1-7.

9. The application of stannous iodide as described in claim 8 in the preparation of perovskite solar cells.

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