Cesium iodide and preparation method thereof, solar cell and preparation method thereof, and photovoltaic module

Abstract

The invention provides cesium iodide and a preparation method thereof, a solar cell and a preparation method thereof, and a photovoltaic module, and the cesium iodide comprises a first substance with reducibility. The cesium iodide provided by the invention is good in stability and easy to store, and the solar cell prepared from the cesium iodide provided by the invention has improved photoelectric conversion efficiency and device stability.

Description

Technical Field

[0001] This application relates to the field of photovoltaic cell technology, and in particular to a cesium iodide and its preparation method, a solar cell and its preparation method, and a photovoltaic module. Background Technology

[0002] In recent years, with the large-scale development and utilization of non-renewable energy sources such as coal and oil, their reserves have become insufficient to meet the needs of various industries, including agriculture and industry. Therefore, renewable energy has gradually become one of the alternative energy sources to non-renewable energy sources, driving social and industrial development. Among these, solar cells (also known as photovoltaic cells) are widely used due to their green and environmentally friendly characteristics, as well as their ability to generate electricity when exposed to sunlight.

[0003] However, in related technologies, the photoelectric conversion efficiency and device stability of solar cell devices still need to be further improved. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide cesium iodide and its preparation method, a solar cell and its preparation method, and a photovoltaic module. The cesium iodide in this application has good stability and is easy to store, and the solar cell prepared using the cesium iodide of this application has improved photoelectric conversion efficiency and device stability.

[0005] To achieve the above objectives, a first aspect of this application provides cesium iodide comprising a first substance having reducing properties.

[0006] The cesium iodide of this application contains a reducing first substance, which makes the cesium iodide less susceptible to oxidation during storage, facilitating preservation and improving its stability. Furthermore, when the cesium iodide containing the reducing first substance is used to prepare the perovskite light-absorbing layer of a solar cell, it improves the thin film quality of the perovskite light-absorbing layer, thereby enhancing the photoelectric conversion efficiency and device stability of the solar cell.

[0007] In some embodiments, the first substance includes one or more of hypophosphite ions, phosphite ions, sulfite ions, bisulfite ions, tetrathionite ions, oxalate ions, and L-ascorbic acid. All of the above-mentioned first substances have reducing properties and can reduce oxidized substances in cesium iodide, such as elemental iodine, thereby improving the stability of cesium iodide.

[0008] In some embodiments, the first substance includes hypophosphite ions and / or L-ascorbic acid. The hypophosphite ions and / or L-ascorbic acid in cesium iodide can, on the one hand, reduce the oxidized iodine in cesium iodide, improving its stability; on the other hand, they can also regulate the crystallization process of the perovskite light-absorbing layer, improving crystal quality. Therefore, the hypophosphite ions and / or L-ascorbic acid in cesium iodide can further improve the photoelectric conversion efficiency and device stability of solar cells.

[0009] In some embodiments, the first substance comprises 0.01% to 1.5% of the cesium iodide in molar proportion. This allows for the improvement of the stability of cesium iodide without affecting its role in enhancing stability and optimizing photoelectric properties within the perovskite light-absorbing layer.

[0010] In some embodiments, the first substance comprises 0.02% to 0.25% of the cesium iodide in molar proportion. This is more advantageous in improving the stability of cesium iodide without affecting its role in enhancing stability and optimizing photoelectric properties in the perovskite light-absorbing layer.

[0011] In some embodiments, the cesium iodide further includes a second substance; the second substance comprises an anion containing N, O, S, P, or a halogen. The N, O, S, P, and halogen atoms in the second substance of cesium iodide possess lone pairs of electrons, and therefore tend to react with uncoordinated Lewis acids such as Pb in the perovskite precursor solution. 2+ Sn 2+ Early coordination can intervene in the coordination or complexation between precursors and between precursors and solvents, delaying the crystallization process of lead and / or tin, improving the crystal quality of the perovskite light-absorbing layer, and thus improving the photoelectric conversion efficiency of solar cells.

[0012] In some embodiments, the second substance includes one or more of nitrate ions, perchlorate ions, acetate ions, benzenesulfonate ions, formate ions, citrate ions, acrylate ions, salicylate ions, phosphate ions, bromide ions, and thiocyanate ions. All of the above-mentioned second substances can regulate the crystallization process of the perovskite light-absorbing layer, improve the crystal quality of the perovskite light-absorbing layer, and thus improve the photoelectric conversion efficiency of the solar cell.

[0013] In some embodiments, the second substance comprises 0.001% to 0.45% of the cesium iodide in the perovskite light-absorbing layer. This allows for improved crystallinity of the perovskite light-absorbing layer without affecting the role of cesium iodide in enhancing stability and optimizing photoelectric properties within the perovskite light-absorbing layer.

[0014] In some embodiments, the second substance comprises 0.005% to 0.015% of the cesium iodide in the perovskite light-absorbing layer. This is more advantageous in improving the crystallinity of the perovskite light-absorbing layer without affecting the role of cesium iodide in enhancing stability and optimizing photoelectric properties within the perovskite light-absorbing layer.

[0015] The second aspect of this application provides a method for preparing cesium iodide, comprising the following steps: S1, preparing an iodine-containing solution and a cesium salt solution, wherein the iodine-containing solution includes a first additive with reducing properties; S2, mixing the iodine-containing solution and the cesium salt solution and stirring to obtain a cesium iodide solution; S3, purifying the cesium iodide solution to obtain cesium iodide. In this application, the addition of a first additive with reducing properties to the iodine-containing solution allows for the reduction of elemental iodine in the iodine-containing solution, thus easily removing elemental iodine, simplifying the synthesis process, and reducing synthesis costs. Furthermore, the reducing ions in the first additive remain as the first substance in the cesium iodide, making the cesium iodide less susceptible to oxidation during storage, easier to preserve, and improving the stability of the cesium iodide.

[0016] When cesium iodide is used in solar cells, it helps to improve the quality and stability of the perovskite light-absorbing layer film, thereby improving the photoelectric conversion efficiency of the solar cell.

[0017] In some embodiments, the first additive includes one or more of hypophosphite, sodium hypophosphite, sodium bisulfite, sodium sulfite, sulfurous acid, oxalic acid, sodium thiosulfate, and L-ascorbic acid. The aforementioned first additive has strong reducing properties, enabling it to reduce elemental iodine in iodine-containing solutions. This simplifies the synthesis process, reduces synthesis costs, and improves the stability of the synthesized cesium iodide.

[0018] In some embodiments, the first additive includes sodium hypophosphite and / or L-ascorbic acid. Sodium hypophosphite and / or L-ascorbic acid not only possess strong reducing properties, enabling them to reduce oxidized iodine in iodine-containing solutions, thus improving the synthesis process of cesium iodide and reducing synthesis costs, but they can also regulate the crystallization process of the perovskite light-absorbing layer, improving crystal quality. Therefore, using sodium hypophosphite and / or L-ascorbic acid as the first additive is beneficial for further improving the photoelectric conversion efficiency of solar cells.

[0019] In some embodiments, the first additive has a molar percentage of 0.01% to 6% in the iodine-containing solution. This allows for the reduction of elemental iodine in the iodine-containing solution without affecting the synthesis of cesium iodide materials.

[0020] In some embodiments, the first additive accounts for 2% to 3% of the molar proportion in the iodine-containing solution. This further facilitates the reduction of elemental iodine in the iodine-containing solution without affecting the synthesis of cesium iodide materials.

[0021] In some embodiments, step S1 includes adding the first additive to an iodine-containing compound solution to obtain the iodine-containing solution; the iodine-containing compound includes hydroiodic acid and / or calcium iodide. In the preparation of cesium iodide, adding the reducing first additive to the iodine-containing compound solution allows for preferential reduction of elemental iodine in the solution, thus simplifying the preparation process and improving the purity and stability of the subsequently formed cesium iodide.

[0022] In some embodiments, the iodine-containing compound includes hydroiodic acid. Hydroiodic acid is readily oxidized to elemental iodine in air, and the first additive can reduce the elemental iodine in the hydroiodic acid back to hydroiodic acid, facilitating subsequent reactions.

[0023] In some embodiments, before performing step S2, the iodine-containing solution is allowed to stand at 2°C to 8°C in the dark for 4 to 6 hours. Allowing the iodine-containing solution to stand under these conditions allows the first additive to react with the iodine-containing compound to a suitable degree, and also prevents the iodine-containing compound in the solution from being oxidized.

[0024] In some embodiments, step S1 further includes dissolving the cesium salt in a solvent under an inert gas atmosphere to obtain the cesium salt solution. Dissolving the cesium salt under an inert gas atmosphere prevents the introduction of oxygen into the cesium salt solution, thus preventing the oxidation of iodine-containing compounds during subsequent reactions.

[0025] In some embodiments, the cesium salt includes one or more of cesium carbonate, cesium hydroxide, and cesium oxide.

[0026] In some embodiments, step S1 further includes adding a second additive to the cesium salt solution and stirring at 2°C to 8°C for 0.5 to 1 hour. Adding the second additive under these conditions allows for more thorough mixing with the cesium salt and promotes preferential reaction, which is beneficial for introducing specific elements from the second additive into the subsequently prepared cesium iodide.

[0027] In some embodiments, the second additive comprises an anion containing nitrogen (N), oxygen (O), sulfur (S), phosphorus (P), a halide ion, or a pseudohalogen ion. Anions containing nitrogen (N), oxygen (O), sulfur (S), phosphorus (P), or a halide ion possess lone pairs of electrons, and therefore tend to react more readily with uncoordinated Lewis acids such as Pb in the perovskite precursor solution. 2+ Sn 2+Early coordination can intervene in the coordination or complexation between precursors and between precursors and solvents, delaying the crystallization process of lead and / or tin, improving the crystal quality of the perovskite light-absorbing layer, and thus improving the photoelectric conversion efficiency of solar cells.

[0028] In some embodiments, the second additive includes one or more of dilute nitric acid, perchloric acid, acetic acid, dodecylbenzenesulfonic acid, 4-chlorobenzenesulfonic acid, benzenesulfonic acid, formic acid, citric acid, acrylic acid, salicylic acid, thiocyanate, hydrobromic acid, and phosphoric acid. All of the above-mentioned second additives can regulate the crystallization process of the perovskite light-absorbing layer, improve the crystal quality of the perovskite light-absorbing layer, and thus improve the photoelectric conversion efficiency of the solar cell.

[0029] In some embodiments, the molar mass percentage of the second additive in the cesium salt solution is 1% to 10%. This allows for the control of the crystallization process of the perovskite light-absorbing layer without affecting the synthesis of cesium iodide materials.

[0030] In some embodiments, the molar mass percentage of the second additive in the cesium salt solution is 2% to 3%. This helps to control the crystallization process of the perovskite light-absorbing layer without affecting the synthesis of cesium iodide materials.

[0031] In some embodiments, in step S2, the stirring process is carried out at 0°C to 10°C for 2 to 4 hours. Under these conditions, the stirring process facilitates the reaction between the iodine-containing solution and the cesium salt, promoting the formation of cesium iodide.

[0032] In some embodiments, step S3 includes evaporation, filtration, and drying. This allows for the acquisition of cesium iodide with high purity.

[0033] In some embodiments, the evaporation process includes evaporating and removing the solvent from the cesium iodide mixture to obtain unpurified cesium iodide.

[0034] In some embodiments, the filtration process includes heating and dissolving the unpurified cesium iodide and filtering it to obtain a cesium iodide mother liquor, cooling and filtering the cesium iodide mother liquor to obtain treated cesium iodide, and then washing and filtering the treated cesium iodide with an alcohol solution to obtain purified cesium iodide. In this application, recrystallization is used to purify cesium iodide, making it more difficult for the second additive to enter the cesium iodide crystal lattice, thereby improving the purity of cesium iodide.

[0035] In some embodiments, the cooling process involves cooling to 2°C to 8°C at a rate of 5°C / min to 12°C / min. This facilitates the rapid recrystallization and precipitation of cesium iodide.

[0036] In some embodiments, the drying process includes vacuum drying the purified cesium iodide at 50°C to 80°C for 8 to 12 hours. This allows the cesium iodide to dry more thoroughly and reduces its contact with air, thereby preventing iodine oxidation.

[0037] A third aspect of this application provides a solar cell, comprising a first electrode, a perovskite light-absorbing layer, and a second electrode arranged sequentially along the light incident direction. The perovskite light-absorbing layer is prepared from cesium iodide according to any one of claims 1 to 9, or from cesium iodide prepared according to the method of any one of claims 10 to 30. Because the solar cell in this application uses cesium iodide, a reducing agent, and cesium iodide has high stability, the perovskite light-absorbing layer film has high quality and stability, which is beneficial for improving the photoelectric conversion efficiency and device stability of the solar cell.

[0038] In some embodiments, the average grain size of the perovskite material in the perovskite light-absorbing layer is 200 nm to 2 μm. This helps to reduce nonradiative recombination at grain boundaries, thereby improving the quality of the perovskite light-absorbing layer film and ultimately increasing the photoelectric conversion efficiency of the solar cell device.

[0039] In some embodiments, a first transport layer and a second transport layer are further included; the first transport layer is located between the first electrode and the perovskite light-absorbing layer; and the second transport layer is located between the perovskite light-absorbing layer and the second electrode.

[0040] The fourth aspect of this application provides a method for fabricating a solar cell, comprising the following steps: S1, forming a first electrode for receiving incident light; S2, coating the first electrode with a perovskite precursor solution to form a perovskite light-absorbing layer; wherein the perovskite precursor solution comprises cesium iodide according to any one of claims 1 to 10, or comprises cesium iodide prepared according to the preparation method according to any one of claims 11 to 31; S3, forming a second electrode on the perovskite light-absorbing layer.

[0041] In this application, cesium iodide, a reducing agent, is used when preparing the perovskite precursor solution. Cesium iodide has high stability, resulting in high quality and stability of the perovskite light-absorbing layer film, which in turn leads to high photoelectric conversion efficiency of the prepared solar cell.

[0042] In some embodiments, the method further includes: forming a first transport layer between the first electrode and the perovskite light-absorbing layer, and forming a second transport layer between the perovskite light-absorbing layer and the second electrode layer.

[0043] In some embodiments, the first transport layer is one of a hole transport layer and an electron transport layer, and the second transport layer is the other of the hole transport layer and the electron transport layer.

[0044] The fifth aspect of this application provides a photovoltaic module, including the solar cell described in the third aspect above, or including a solar cell prepared according to the preparation method described in the fourth aspect above. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the structure of a solar cell provided in one embodiment of this application;

[0046] Figure 2 This is an XRD pattern of cesium iodide in Example 1 of this application.

[0047] Explanation of reference numerals in the attached figures:

[0048] Solar cell 10; first electrode 101; first transport layer 102; perovskite light-absorbing layer 103; second transport layer 104; second electrode 105. Detailed Implementation

[0049] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of cesium iodide and its preparation method, solar cells and their preparation methods, and photovoltaic modules of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0050] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0051] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0052] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0053] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0054] Unless otherwise specified, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0055] Unless otherwise specified, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, according to the testing methods given in this application.

[0056] As a new photovoltaic technology for the future, solar cells have made remarkable progress, but the photoelectric conversion efficiency of solar cell devices still needs further improvement. The perovskite light-absorbing layer, as a crucial component of solar cells, directly impacts the photoelectric conversion efficiency of solar cell devices.

[0057] Cesium iodide is one of the important raw materials for preparing perovskite light-absorbing layers. In the conventional synthesis of cesium iodide, the hydroiodic acid used is easily oxidized to elemental iodine during the synthesis process, resulting in poor stability of the synthesized cesium iodide. It is easily degraded by external influences. Therefore, the stability of perovskite light-absorbing layers prepared with cesium iodide as a raw material is also poor, leading to low photoelectric conversion efficiency and device stability of solar cells.

[0058] Based on this, embodiments of this application provide a novel cesium iodide and its preparation method, a solar cell and its preparation method, and a photovoltaic module. The cesium iodide in this application exhibits good stability and is easy to store, and the solar cell prepared using the cesium iodide of this application has improved photoelectric conversion efficiency and device stability.

[0059] Cesium iodide

[0060] A first aspect of this application provides cesium iodide, comprising a first substance having reducing properties.

[0061] The cesium iodide of this application contains a reducing first substance, which makes the cesium iodide less susceptible to oxidation during storage, facilitating preservation and improving its stability. Furthermore, when the cesium iodide containing the reducing first substance is used to prepare the perovskite light-absorbing layer of a solar cell, it improves the thin film quality of the perovskite light-absorbing layer, thereby enhancing the photoelectric conversion efficiency and device stability of the solar cell.

[0062] In some embodiments, the first substance includes one or more of hypophosphite ions, phosphite ions, sulfite ions, bisulfite ions, tetrathionite ions, oxalate ions, and L-ascorbic acid. All of the above-mentioned first substances have reducing properties and can reduce oxidized substances in cesium iodide, such as elemental iodine, thereby improving the stability of cesium iodide.

[0063] It should be noted that the main phase in the cesium iodide provided in this application is cesium iodide, and the content of the first substance in cesium iodide is relatively small. For example, the molar percentage of the first substance in cesium iodide is less than or equal to 1.5%.

[0064] It should also be noted that the hypophosphite, phosphite, sulfite, bisulfite, tetrathionate, and oxalate ions in the first substance all exist in the form of cesium salts in cesium iodide. For example, hypophosphite exists as cesium hypophosphite, phosphite as cesium phosphite, sulfite as cesium sulfate, bisulfite as cesium bisulfite, tetrathionate as cesium tetrathionate, and oxalate as cesium oxalate.

[0065] In some embodiments, the first substance includes hypophosphite ions and / or L-ascorbic acid. The hypophosphite ions and / or L-ascorbic acid in cesium iodide can, on the one hand, reduce the oxidized iodine in cesium iodide, improving its stability; on the other hand, they can also regulate the crystallization process of the perovskite light-absorbing layer, improving crystal quality. Therefore, the hypophosphite ions and / or L-ascorbic acid in cesium iodide can further improve the photoelectric conversion efficiency and device stability of solar cells.

[0066] In some embodiments, the molar percentage of the first substance in cesium iodide is 0.01% to 1.5%; optionally, it is 0.01% to 0.3%, and more preferably, it is 0.02% to 0.25%. Exemplarily, the molar percentage of the first substance in cesium iodide is 0.01%, 0.02%, 0.05%, 0.1%, 0.2%, 0.25%, 0.3%, 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, or a value within a range of any two of these values. Thus, it is possible to improve the stability of cesium iodide without affecting its role in improving stability and optimizing photoelectric properties in the perovskite light-absorbing layer.

[0067] In some embodiments, cesium iodide further includes a second substance comprising an anion containing nitrogen (N), oxygen (O), sulfur (S), phosphorus (P), or a halogen. The N, O, S, P, and halogen atoms in the second substance of cesium iodide possess lone pairs of electrons, and therefore tend to react more readily with uncoordinated Lewis acids such as Pb in the perovskite precursor solution. 2+ Sn 2+ Early coordination can intervene in the coordination or complexation between precursors and between precursors and solvents, delaying the crystallization process of lead and / or tin, improving the crystal quality of the perovskite light-absorbing layer, and thus improving the photoelectric conversion efficiency of solar cells.

[0068] In some embodiments, the second substance includes one or more of the following: nitrate ions, perchlorate ions, acetate ions, benzenesulfonate ions, formate ions, citrate ions, acrylate ions, salicylate ions, phosphate ions, bromide ions, and thiocyanate ions. All of these second substances can regulate the crystallization process of the perovskite light-absorbing layer, improve the crystal quality of the perovskite light-absorbing layer, and thus improve the photoelectric conversion efficiency of the solar cell.

[0069] It should be noted that the secondary substance in cesium iodide mainly exists in the form of cesium salts. For example, nitrate ions mainly exist in the form of cesium nitrate, perchlorate ions mainly exist in the form of cesium perchlorate, acetate ions mainly exist in the form of cesium acetate, benzenesulfonate ions mainly exist in the form of cesium benzenesulfonate, formate ions mainly exist in the form of cesium formate, citrate ions mainly exist in the form of cesium citrate, acrylate ions mainly exist in the form of cesium acrylate, salicylate ions mainly exist in the form of cesium salicylate, phosphate ions mainly exist in the form of cesium phosphate, bromide ions mainly exist in the form of cesium bromide, and thiocyanate ions mainly exist in the form of cesium thiocyanate.

[0070] In some embodiments, the molar percentage of the second substance in cesium iodide is 0.001% to 0.45%; optionally, it is 0.005% to 0.2%, and more preferably, it is 0.005% to 0.015%. Exemplarily, the molar percentage of the second substance in cesium iodide is 0.001%, 0.003%, 0.005%, 0.01%, 0.015%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.45%, or a value within a range of any two of these values. Therefore, it is possible to improve the crystallinity of the perovskite light-absorbing layer without affecting the role of cesium iodide in improving stability and optimizing photoelectric properties within the perovskite light-absorbing layer.

[0071] In this application, the first substance, the second substance, and the content of the first substance and the second substance in cesium iodide can all be detected by conventional methods in the art, such as ion chromatography. Specifically, the prepared cesium iodide sample is dissolved in deionized water, and a 14 mM potassium hydroxide aqueous solution is used as the mobile phase in the chromatographic column of an ion chromatograph to separate the major and minor anions in the cesium iodide sample aqueous solution. Qualitative analysis is then performed by measuring the retention time in the chromatographic column. Quantitative analysis is then performed by utilizing the linear relationship between the peak area of ​​the tested ion and the concentration of the standard liquid.

[0072] Preparation method of cesium iodide

[0073] The second aspect of this application provides a step for preparing cesium iodide, comprising the following steps: S1, preparing an iodine-containing solution and a cesium salt solution, wherein the iodine-containing solution includes a first additive with reducing properties; S2, mixing the iodine-containing solution and the cesium salt solution and stirring to obtain a cesium iodide solution; S3, purifying the cesium iodide solution to obtain cesium iodide.

[0074] In this application, a first additive with reducing properties is added to an iodine-containing solution. This first additive can reduce the elemental iodine in the iodine-containing solution, thus easily removing the elemental iodine, simplifying the synthesis process, and reducing synthesis costs. Furthermore, the reducing ions in the first additive remain as the first substance in cesium iodide, making cesium iodide less susceptible to oxidation during storage, easier to preserve, and improving the stability of cesium iodide.

[0075] When cesium iodide is used in solar cells, it helps to improve the quality and stability of the perovskite light-absorbing layer film, thereby improving the photoelectric conversion efficiency of the solar cell.

[0076] In some embodiments, the first additive includes one or more of hypophosphite, sodium hypophosphite, sodium bisulfite, sodium sulfite, sulfurous acid, oxalic acid, sodium thiosulfate, and L-ascorbic acid. The aforementioned first additive has strong reducing properties, enabling it to reduce elemental iodine in iodine-containing solutions. This simplifies the synthesis process, reduces synthesis costs, and improves the stability of the synthesized cesium iodide.

[0077] In some embodiments, the first additive includes sodium hypophosphite and / or L-ascorbic acid. Sodium hypophosphite and / or L-ascorbic acid not only possess strong reducing properties, enabling them to reduce oxidized iodine in iodine-containing solutions, thus improving the synthesis process of cesium iodide and reducing synthesis costs, but they can also regulate the crystallization process of the perovskite light-absorbing layer, improving crystal quality. Therefore, using sodium hypophosphite and / or L-ascorbic acid as the first additive is beneficial for further improving the photoelectric conversion efficiency of solar cells.

[0078] In some embodiments, the molar percentage of the first additive in the iodine-containing solution is 0.01% to 6%; optionally, it is 2% to 3%. Exemplarily, the molar percentage of the first additive in the iodine-containing solution is a value within the range of 0.01%, 0.03%, 0.05%, 0.08%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 2.8%, 2.9%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, or any two of these values. Therefore, it is possible to reduce elemental iodine in the iodine-containing solution without affecting the synthesis of cesium iodide materials.

[0079] In some embodiments, step S1 includes adding a first additive to an iodine-containing compound solution to obtain an iodine-containing solution; the iodine-containing compound includes hydroiodic acid and / or calcium iodide. In the preparation of cesium iodide, adding a reducing first additive to the iodine-containing compound solution allows for preferential reduction of elemental iodine in the solution, thus simplifying the preparation process and improving the purity and stability of the subsequently formed cesium iodide.

[0080] In some embodiments, the iodine-containing compound includes hydroiodic acid. Hydroiodic acid is readily oxidized to elemental iodine in air, and the first additive can reduce the elemental iodine in hydroiodic acid back to hydroiodic acid, facilitating subsequent reactions.

[0081] In some embodiments, before performing step S2, the iodine-containing solution is allowed to stand in the dark at 0°C to 10°C for 4 to 12 hours; alternatively, the iodine-containing solution is allowed to stand in the dark at 2°C to 8°C for 8 to 10 hours. Allowing the iodine-containing solution to stand under the above conditions allows the first additive to react with the iodine-containing compound to a suitable degree, and also prevents the iodine-containing compound in the iodine-containing solution from being oxidized.

[0082] In some embodiments, step S1 further includes dissolving the cesium salt in a solvent under an inert gas atmosphere to obtain a cesium salt solution. Optionally, the inert gas may be, for example, argon, krypton, or xenon; more preferably, the inert gas may be argon. Dissolving the cesium salt under an inert gas atmosphere does not introduce oxygen into the cesium salt solution, thus preventing the oxidation of iodine-containing compounds during subsequent reactions.

[0083] In some embodiments, the solvent for dissolving the cesium salt solution includes deionized water or an organic solvent; for example, the organic solvent includes ethanol; alternatively, the solvent includes deionized water.

[0084] In some embodiments, the cesium salt includes one or more of cesium carbonate, cesium hydroxide, and cesium oxide; alternatively, the cesium salt includes cesium carbonate.

[0085] In some embodiments, step S1 further includes adding the second additive to the cesium salt solution and stirring at 2°C to 8°C for 0.5 to 1 hour, or optionally, stirring at 4°C to 6°C for 0.5 hours. Adding the second additive under these conditions allows for more thorough mixing with the cesium salt and promotes preferential reaction, which is beneficial for introducing specific elements from the second additive into the subsequently prepared cesium iodide.

[0086] In some embodiments, the second additive comprises an anion containing nitrogen (N), oxygen (O), sulfur (S), phosphorus (P), a halide ion, or a pseudohalogen ion. Anions containing nitrogen (N), oxygen (O), sulfur (S), phosphorus (P), or a halide ion possess lone pairs of electrons, and therefore tend to react more readily with uncoordinated Lewis acids such as Pb in the perovskite precursor solution. 2+ Sn 2+ Early coordination can intervene in the coordination or complexation between precursors and between precursors and solvents, delaying the crystallization process of lead and / or tin, improving the crystal quality of the perovskite light-absorbing layer, and thus improving the photoelectric conversion efficiency of solar cells.

[0087] In some embodiments, the nitrogen-containing anion includes one or more of nitrate ions, thiocyanate ions, cyanate ions, selenocyanate ions, and oxycyanate ions. Correspondingly, the second additive may be, for example, dilute nitric acid, thiocyanic acid, or thiocyanate. For example, thiocyanate may be sodium thiocyanate.

[0088] In some embodiments, the anions containing oxygen (O) include formate, acetate, acrylate, citrate, and salicylate ions. Correspondingly, the second additive may be, for example, formic acid, acetic acid, acrylic acid, acrylate, citric acid, citrate, salicylic acid, or salicylate. For example, the acrylate may be sodium acrylate.

[0089] In some embodiments, the sulfur-containing anion includes benzenesulfonate ions. Correspondingly, the second additive may be one or more of benzenesulfonic acid, benzenesulfonate, dodecylbenzenesulfonic acid, and 4-chlorobenzenesulfonic acid. For example, benzenesulfonate may be sodium benzenesulfonate.

[0090] In some embodiments, the anion containing phosphorus includes phosphate ions. Correspondingly, the second additive may be, for example, phosphoric acid.

[0091] In some embodiments, the halogen-containing acid anions include perchlorate and bromide ions. Correspondingly, the second additive may be one or more of perchloric acid, perchlorate, and hydrobromic acid.

[0092] In some embodiments, the second additive includes one or more of dilute nitric acid, perchlorate, acetic acid, dodecylbenzenesulfonic acid, 4-chlorobenzenesulfonic acid, benzenesulfonic acid, formic acid, citric acid, acrylic acid, salicylic acid, phosphoric acid, thiocyanate, and hydrobromic acid. All of the above-mentioned second additives can regulate the crystallization process of the perovskite light-absorbing layer, improve the crystal quality of the perovskite light-absorbing layer, and thus improve the photoelectric conversion efficiency of the solar cell.

[0093] In some embodiments, the molar mass percentage of the second additive in the cesium salt solution is 1% to 10%, optionally 2% to 3%. Exemplarily, the molar percentage of the second additive in the cesium salt solution is a value within the range of 1%, 2%, 2.8%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any two of these values. Therefore, it is possible to control the crystallization process of the perovskite light-absorbing layer without affecting the synthesis of the cesium iodide material.

[0094] In some embodiments, in step S2, the stirring process is carried out at 0°C to 10°C for 2 to 4 hours, or optionally at 2°C to 8°C for 4 hours. Under these conditions, the stirring process facilitates the reaction between the iodine-containing solution and the cesium salt, promoting the formation of cesium iodide.

[0095] In some embodiments, step S2, mixing the iodine-containing solution with the cesium salt solution, includes adding the iodine-containing solution separately to the cesium salt solution. This allows control over the formation rate of cesium iodide.

[0096] In some embodiments, step S3 includes evaporation, filtration, and drying. Through this purification process, cesium iodide with high purity can be obtained.

[0097] In some embodiments, the evaporation process includes evaporating the solvent from the cesium iodide mixture to obtain unpurified cesium iodide.

[0098] In some embodiments, the filtration process includes heating and dissolving unpurified cesium iodide and filtering to obtain a cesium iodide mother liquor, cooling and filtering the cesium iodide mother liquor to obtain treated cesium iodide, and then washing and filtering the treated cesium iodide with an alcohol solution to obtain purified cesium iodide. In this application, cesium iodide is purified by recrystallization, which makes it more difficult for the second additive to enter the cesium iodide crystal lattice, thereby improving the purity of cesium iodide; in addition, during the purification process, a small amount of the first additive adsorbs onto the surface of cesium iodide, encapsulating the cesium iodide and improving the stability of the prepared cesium iodide.

[0099] In some embodiments, the cooling process involves cooling to 0°C to 10°C at a rate of 5°C / min to 12°C / min; alternatively, the cooling process involves cooling to 2°C to 8°C at a rate of 7°C / min to 10°C / min. Cooling under these conditions facilitates the rapid recrystallization of cesium iodide.

[0100] In some embodiments, the drying process includes vacuum drying the purified cesium iodide at 50°C to 80°C for 8 to 12 hours, or optionally, drying at 60°C to 70°C for 6 to 8 hours. Performing the drying process under these conditions ensures that the cesium iodide is dried more thoroughly and reduces its contact with air, thereby preventing the iodine from being oxidized.

[0101] Solar cells

[0102] A third aspect of the embodiments of this application provides a solar cell, Figure 1 A schematic diagram of the structure of a solar cell provided in one embodiment of this application is shown below. Figure 1 As shown, the solar cell 10 includes a first electrode 101, a perovskite light-absorbing layer 103, and a second electrode 105 arranged sequentially along the light incident direction; the raw material for preparing the perovskite light-absorbing layer includes cesium iodide as described in the first aspect above, or includes cesium iodide prepared according to the preparation method of the second aspect above.

[0103] The solar cell in this application uses cesium iodide, a reducing agent, which has high stability. This results in a high quality and stability of the perovskite light-absorbing layer film, which is beneficial for improving the photoelectric conversion efficiency and device stability of the solar cell.

[0104] In some embodiments, the average grain size of the perovskite material in the perovskite light-absorbing layer 103 is 200 nm to 2 μm. An average grain size within this range is beneficial for reducing non-radiative recombination at grain boundaries, thereby improving the quality of the perovskite light-absorbing layer film and ultimately increasing the photoelectric conversion efficiency of the solar cell device.

[0105] In this application, the grain size of the perovskite material can be measured in the following way: the surface morphology of the perovskite light-absorbing layer is tested using a scanning electron microscope (Hitachi, HD-2700), and the grain size of the perovskite material is measured based on the tested scanning electron microscope image. Then, the average grain size of the perovskite material is obtained by averaging.

[0106] In some embodiments, the thickness of the perovskite light-absorbing layer is from 200 nm to 700 nm, and optionally, the thickness is from 400 nm to 600 nm. A thickness within this range is beneficial for improving light absorption utilization and increasing the efficiency of the solar cell device.

[0107] In some embodiments, the first electrode 101 refers to the electrode that first receives incident light and is used to collect electrons / holes; the second electrode 105 refers to the electrode that last receives incident light and is used to collect holes / electrons.

[0108] In some embodiments, the electrode material of the first electrode 101 includes one or more of organic conductive materials, inorganic conductive materials, or organic-inorganic mixed conductive materials. Optionally, it includes one or more of transparent conductive metal oxides, carbon, metals and their alloys. More preferably, it includes at least one of indium tin oxide (ITO), lanthanide-doped indium oxide, fluorine-doped tin oxide (FTO), antimony-doped tin oxide, boron-doped zinc oxide (BZO), zinc aluminum oxide (AZO), indium zinc oxide (IZO), zinc gallium oxide (GZO), indium tungsten oxide (IWO), Au, Ag, Cu, Al, Ni, Cr, Bi, Pt, Mg, Mo, W and their alloys, graphite, graphene, and carbon nanotubes. Optionally, it includes at least one of Ag, Cu, C, Au, Al, ITO, AZO, BZO, or IZO. Further, it includes at least one of Cu, Ag, and Au.

[0109] In some embodiments, the electrode material of the second electrode 105 includes transparent conductive oxides, metals, etc. The transparent conductive oxides include one or more of indium tin oxide (ITO), lanthanide metal-doped indium oxide, fluorine-doped tin oxide (FTO), antimony-doped tin oxide, boron-doped zinc oxide (BZO), aluminum zinc oxide (AZO), indium zinc oxide (IZO), gallium zinc oxide (GZO), and indium tungsten oxide (IWO). The metals include one or more of Au, Ag, Cu, Al, Ni, Cr, Bi, Pt, and Mg.

[0110] In some embodiments, the perovskite absorbing layer 103 is disposed between the first electrode 101 and the second electrode 105, and electron-hole pairs can be generated based on the excitation of incident light. This application does not impose a particular limitation on the band gap of the perovskite absorbing layer 103; a band gap commonly used in the art for perovskite absorbing layers can be used. For example, the band gap of the perovskite absorbing layer is between 1.20 eV and 2.30 eV. This application does not impose a particular limitation on the band gap measurement method. For example, the band gap measurement method may include: first, obtaining an ultraviolet absorption curve through ultraviolet absorption spectroscopy; and then calculating the band gap of the perovskite absorbing layer using the Tau equation.

[0111] In some embodiments, the perovskite light-absorbing layer comprises at least one of the compounds shown in [A][B][X]3 and [A]2[C][D][X]6, wherein A comprises at least one monovalent inorganic or organic cation, B comprises at least one divalent inorganic cation, C comprises at least one monovalent inorganic cation, D comprises at least one trivalent inorganic cation, and X comprises at least one monovalent anion.

[0112] For example, organic cations include: CH(NH2)2 +(abbreviated as FA) + CH3NH3 + (abbreviated as MA) + At least one of the following. Exemplary inorganic cations include: Li + Na + K + 、Rb + Cs + Pb 2+ Sn 2+ Be 2+ Mg 2+ Ca 2+ 、Sr 2+ Ba 2+ Zn 2+ 、Ge 2+ Fe 2+ Co 2+ Ni 2+ At least one of the following. Exemplary inorganic anions include: F - Cl - ,Br - I - SCN - CNO - OCN - OSCN - SH - OH - CN - SeCN - N3 - At least one of them.

[0113] In some embodiments, A is selected from cations with larger radii; for example, cations with larger radii include MA. + FA + Li + Na + K + 、Rb + Cs + At least one of them. B is selected from cations with smaller radii, for example, cations with smaller radii include Pb. 2+ Sn 2+ Be 2+ Mg 2+ Ca 2+ 、Sr 2+ Ba 2+ Zn 2+ 、Ge 2+ Fe 2+ Co 2+ Ni 2+ At least one of them. X is selected from Cl- ,Br - I - At least one of them.

[0114] In some embodiments, A is selected from monovalent cations. For example, monovalent cations include MA. + FA + Li + Na + K + 、Rb + Cs + At least one of the following. B is selected from divalent metal cations, exemplarily including Pb. 2+ Sn 2+ Be 2+ Mg 2+ Ca 2+ 、Sr 2+ Ba 2+ Zn 2+ 、Ge 2+ Fe 2+ Co 2+ Ni 2+ At least one of them.

[0115] In some implementations, please refer to [the documentation / reference]. Figure 1 The solar cell further includes a first transport layer 102 and a second transport layer 104; the first transport layer 102 is located between the first electrode 101 and the perovskite light-absorbing layer 103; the second transport layer 104 is located between the perovskite light-absorbing layer 103 and the second electrode 105.

[0116] In some embodiments, the first transport layer 102 is a hole transport layer and the second transport layer 104 is an electron transport layer; or, the first transport layer 102 is an electron transport layer and the second transport layer 104 is a hole transport layer.

[0117] This application does not impose specific limitations on the hole transport material used in the hole transport layer; hole transport materials commonly used in the art can be employed. Exemplary hole transport materials include poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (Spiro-OMeTAD), poly-3-hexylthiazole (P3HT), triphenylamine with a triphenylene core (H101), 3,4-ethylenedioxythiazole-methoxytriphenylamine (EDOT-OMeTPA), and N-(4-aniline). At least one of the following: carbazole-spirobisfluorene (CzPAF-SBF), poly(3,4-ethylenedioxythiazole): poly(styrene sulfonate) (PEDOT:PSS), polythiazole, nickel oxide (NiOx), molybdenum oxide (MoO3), cuprous iodide (CuI), cuprous oxide (CuO), [2-(9H-carbazole-9-yl)ethyl]phosphonic acid (2PACz), and [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid (Me-4PACz).

[0118] This application does not specifically limit the electron transport material used in the electron transport layer; commonly used electron transport materials in the art can be used. For example, electron transport materials include at least one of imide compounds, quinone compounds, fullerenes and their derivatives, metal oxides, semiconductor oxides, titanates, fluorides and their derivatives, and materials obtained by doping or passivation. Exemplarily, imide compounds include at least one of phthalimide, succinimide, N-bromosuccinimide, glutarimide, or maleimide. Exemplarily, quinone compounds include at least one of benzoquinone, naphthoquinone, phenanthrenequinone, or anthraquinone. Exemplarily, fullerenes and their derivatives include fullerene C... 60 Fullerene C 70、 PCBM ([6,6]-phenyl-C61-butyrate methyl ester), [6,6]-phenyl-C 71 Methyl butyrate (PC) 71 At least one of BM. Exemplarily, the metal element in the metal oxide includes at least one of Mg, Cd, Zn, In, Pb, W, Sb, Bi, Hg, Ti, Ag, Mn, Fe, V, Sn, Zr, Sr, Ga, and Cr; optionally, the metal oxide includes at least one of tin dioxide (SnO2) and zinc oxide (ZnO). Exemplarily, the semiconductor material oxide includes silicon oxide. Exemplarily, the titanate includes at least one of strontium titanate and calcium titanate. Exemplarily, the fluoride includes at least one of lithium fluoride and calcium fluoride.

[0119] In some embodiments, the solar cell 10 further includes a buffer layer (not shown) located on the side of the electron transport layer away from the perovskite light-absorbing layer.

[0120] In some embodiments, the material of the buffer layer may include at least one of fullerene and its derivatives, SnO2 (1.5≤z≤2), and copper bath (BCP).

[0121] In some embodiments, the solar cell 10 includes a lead-based perovskite solar cell, a tin-based perovskite solar cell, or a tin-lead hybrid perovskite solar cell.

[0122] Methods for preparing solar cells

[0123] A fourth aspect of the embodiments of this application provides a method for preparing a solar cell, comprising the following steps:

[0124] S1, forming the first electrode, which is used to receive incident light;

[0125] S2, a perovskite precursor solution is coated on the first electrode to form a perovskite light-absorbing layer; the perovskite precursor solution contains cesium iodide as described in the first aspect above, or contains cesium iodide prepared according to the preparation method of the second aspect above.

[0126] S3 forms a second electrode on the perovskite light-absorbing layer.

[0127] In this application, cesium iodide, a reducing agent, is used when preparing the perovskite precursor solution. Cesium iodide has high stability, resulting in high quality and stability of the perovskite light-absorbing layer film, which in turn leads to high photoelectric conversion efficiency of the prepared solar cell.

[0128] In some embodiments, the concentration of the perovskite precursor solution ranges from 0.8 mol / L to 1.5 mol / L, and optionally from 1.0 mol / L to 1.4 mol / L. This facilitates the preparation of a perovskite light-absorbing layer with a suitable thickness.

[0129] In some embodiments, the method further includes: forming a first transport layer between the first electrode and the perovskite light-absorbing layer, and forming a second transport layer between the perovskite light-absorbing layer and the second electrode layer.

[0130] In some embodiments, the first transport layer is one of a hole transport layer and an electron transport layer, and the second transport layer is the other of the hole transport layer and the electron transport layer.

[0131] In some embodiments, a hole transport solution is coated on the surface of the first electrode and then annealed to form the first transport layer; or, an electron transport solution is vapor-deposited on the surface of the first electrode to form the first transport layer.

[0132] In some embodiments, an electron transport solution is vapor-deposited onto the surface of the perovskite light-absorbing layer to form a second transport layer, or a hole transport solution is coated onto the surface of the perovskite light-absorbing layer and then annealed to form a second transport layer.

[0133] In some embodiments, the method further includes forming a buffer layer located on the side of the first or second transport layer away from the perovskite light-absorbing layer. The buffer layer can effectively prevent holes from moving to the second electrode, improving the photoelectric conversion efficiency of the perovskite solar cell.

[0134] photovoltaic modules

[0135] A fifth aspect of the embodiments of this application also provides a photovoltaic module. Typically, a photovoltaic module includes the aforementioned solar cells, solder strips connecting multiple solar cells, a junction box for current transmission, and a cell encapsulation component.

[0136] In some embodiments, the battery encapsulation component includes photovoltaic glass, which covers the aforementioned solar cell and serves to protect it. Simultaneously, the photovoltaic glass possesses excellent light transmittance and high hardness, allowing it to withstand large diurnal temperature variations and harsh weather conditions.

[0137] In some embodiments, the battery encapsulation component includes an ethylene-vinyl acetate copolymer (EVA) film disposed between the photovoltaic glass and the solar cell for bonding the photovoltaic glass and the solar cell.

[0138] In some implementations, the battery encapsulation components include a photovoltaic backsheet, which also serves to protect the solar cells.

[0139] Optionally, the photovoltaic backsheet can be made of polyvinyl fluoride composite film or thermoplastic elastic material. The photovoltaic backsheet material has properties such as insulation, water resistance, and aging resistance.

[0140] In some implementations, the battery encapsulation component includes a solar aluminum frame, made of aluminum alloy, which features high strength and good corrosion resistance. It serves to support and protect the solar cells.

[0141] Example

[0142] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Unless otherwise stated, all reagents used are commercially available, and all equipment used is conventional equipment.

[0143] Example 1

[0144] Preparation of cesium iodide:

[0145] S1, prepare an iodine-containing solution and a cesium salt solution;

[0146] a) Add 10 ml of the first additive hypophosphite (commercially available with a purity of 50%) to 500 ml of iodine-containing compound hydroiodic acid (commercially available with a concentration of 57%), place it in a refrigerator at 5°C and let it stand for 12 h to obtain an iodine-containing solution of hydroiodic acid, wherein the molar percentage of the first additive hypophosphite in the hydroiodic acid is 2.9%.

[0147] b) Weigh 5g of cesium carbonate and add it to a three-hole flask. Add 20ml of deionized gas and purge with inert argon gas. Place the three-hole flask in an ice-water bath at 5°C and stir for 0.5h to obtain a cesium carbonate solution.

[0148] S2, Measure 4.5 mL of the hydroiodic acid prepared in step a) and add it dropwise to the cesium carbonate solution prepared in step b), stir at 5°C for 2 h, and then return to room temperature.

[0149] S3, purification treatment; c) Heat the reaction solution of step S2 to remove the solvent, and obtain unpurified cesium iodide; d) Add 5 mL of deionized water to the unpurified cesium iodide and heat to dissolve it. When the cesium iodide solution becomes clear, perform the first filtration to remove insoluble impurities, and obtain cesium iodide mother liquor; e) Quickly cool the cesium iodide mother liquor in step d) to precipitate cesium iodide powder, and perform the second filtration to obtain treated cesium iodide; f) Add 3 mL of deionized water to the treated cesium iodide powder and sonicate to dissolve it. Then add the cesium iodide solution dropwise to 50 mL of ethanol to obtain white cesium iodide powder. Separate the white cesium iodide powder and ethanol mixture by vacuum filtration and wash with ethanol to obtain purified cesium iodide; g) Collect the purified cesium iodide obtained in step f) and place it in a vacuum oven at 60°C for vacuum drying for 12 h to obtain cesium iodide.

[0150] Performance parameter testing of cesium iodide:

[0151] 1. Ion chromatography analysis

[0152] The cesium iodide prepared in Example 1 was subjected to ion chromatography analysis to measure the ions (including the first and second substances) in the cesium iodide. Specifically, the prepared cesium iodide sample was dissolved in deionized water, and a 14 mM potassium hydroxide aqueous solution was used as the mobile phase in the chromatographic column of the ion chromatograph. After separating the major and minor anions in the cesium iodide sample aqueous solution, the qualitative analysis was performed by measuring the retention time in the chromatographic column. Then, the quantitative analysis was achieved by utilizing the linear relationship between the peak area of ​​the tested ion and the concentration of the standard liquid. The ion chromatography analysis results are shown in Table 1.

[0153] 2. X-ray diffraction analysis

[0154] X-ray diffraction analysis was performed on the cesium iodide prepared in Example 1. Specifically, the cesium iodide sample was placed in a sample well with a depth of 0.5 mm and a diameter of 25 mm using the plate preparation method. The sample was placed on the sample stage, with CuKα rays as the radiation source and a copper target as the anode target. The 2Theta angle was set to 10°-80°, and the test duration was 10 min. A Bruker D8 Discover X-ray diffractometer was used as the testing instrument.

[0155] Figure 2 The XRD pattern of cesium iodide provided in Example 1 shows that the sample prepared in Example 1 is pure phase cesium iodide.

[0156] 3. Storage performance test

[0157] The cesium iodide prepared in Example 1 was stored under sealed conditions at 25°C for 240 days. After the storage period, the color of the cesium iodide was observed with the naked eye to see if it was still white. If the cesium iodide was still white after storage, it was considered that the cesium iodide had not deteriorated during storage. If the color of the cesium iodide changed to light yellow, dark yellow, yellow or purplish-black after storage, it was considered that the cesium iodide had deteriorated during storage.

[0158] Fabrication of solar cells:

[0159] S1, Fabrication of the first electrode and the first transport layer:

[0160] a. Purchase conductive glass with fluorine-doped tin oxide (FTO) film (Suzhou Shangyang Technology) as the first electrode. Use acetone-alcohol-deionized water to ultrasonically clean the first electrode for 30 minutes in sequence, and then dry the first electrode after cleaning for later use.

[0161] b. Irradiate the cleaned conductive glass (i.e., the first electrode) under an ultraviolet ozone generator for 10 minutes. Weigh 50 mg of nickel nitrate hexahydrate and dissolve it in 1 mL of methanol. Stir the solution for 2 hours using a magnetic stirrer to obtain a light green, transparent, and clear liquid. Filter the solution and take the supernatant. Spin-coat the supernatant onto the first electrode and then anneal it according to the following procedure: hold the temperature at 80°C for 10 minutes, raise the temperature to 345°C within 30 minutes, hold the temperature at 345°C for 30 minutes, and then cool it to 100°C before removing it. The hole transport layer is then obtained as the first transport layer.

[0162] S2, Preparation of the perovskite light-absorbing layer:

[0163] c. Preparation of perovskite precursor solution: Dissolve 26 mg FABr, 27.1 mg MABr, 23.4 mg CsI prepared in Example 1, 167.7 mg FAI, and 691.5 mg PbI2 in 1 mL of a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) with a volume ratio of DMF to DMSO of 4:1. Stir the perovskite precursor solution with a magnetic stirrer at room temperature for 1 h, filter it through a PTFE membrane, and collect the supernatant for later use.

[0164] d. Irradiate the hole transport layer obtained in step S1 under ultraviolet light for 15 min, then drop 60 μL of the supernatant of the perovskite precursor solution onto the hole transport layer, rotate it for 30 s using a spin coater, and anneal it at 150 °C for 1 h to obtain the perovskite light-absorbing layer.

[0165] S3, fabrication of the second transport layer, buffer layer and second electrode;

[0166] e. Add 20 mg of methyl [6,6]-phenyl-C61-butyrate (PCBM, Xi'an Baolai Te) to the solvent chlorobenzene to prepare a PCBM solution with a concentration of 20 mg / ml;

[0167] f. Add 0.5 mg of BCP to the solvent isopropanol to prepare a BCP solution with a concentration of 0.5 mg / ml;

[0168] g. Using a Rebo spin coater, 60 μL of the prepared PCBM solution was spin-coated onto the perovskite light-absorbing layer for 30 s. Then, it was annealed at 100 °C for 10 min. After that, it was removed from the instrument and cooled to room temperature to obtain the electron transport layer.

[0169] h. Spin-coat 60 μL of BCP solution onto the surface of the electron transport layer for 30 s to obtain the buffer layer.

[0170] i. Deposit 80 nm of silver in a vacuum evaporation equipment at a deposition rate of 0.1 A / s to obtain the second electrode.

[0171] By following the above steps, perovskite material Cs can be prepared. 0.05 FA 0.79 MA 0.16 PbI 2.7 Br 0.3 Lead-based perovskite solar cells.

[0172] Photovoltaic parameter testing of solar cells

[0173] 1. Photoelectric conversion efficiency (PCE) test

[0174] Under normal temperature and pressure, a standard AM1.5G solar light source, conforming to the national standard IEC61215, was used for testing. Crystalline silicon solar cells were used to correct the light intensity to achieve a solar intensity. A four-channel digital source meter (Keithley 2440) was used to measure the current-voltage characteristic curve of the solar cells under illumination, obtaining the open-circuit voltage Voc, short-circuit current density Jsc, and fill factor FF.

[0175] Photoelectric conversion efficiency PCE = J SC ·V OC ·FF.

[0176] 2. Device stability determination

[0177] After the photoelectric conversion efficiency test is completed, the solar cell is placed in an atmospheric environment (relative humidity of 65% to 85% and ambient temperature of approximately 15°C to 40°C) and left in the dark for 1000 hours. The photoelectric conversion efficiency is then tested again using the method described above and recorded.

[0178] Normalized efficiency after 1000 hours of storage = Photoelectric conversion efficiency after 1000 hours of storage / Initial photoelectric conversion efficiency * 100%.

[0179] Examples 2-8

[0180] Cesium iodide and solar cells were prepared using the same method as in Example 1, except that the type or amount of the first additive used in the preparation of cesium iodide was different, as specifically adjusted according to Table 1 below.

[0181] Comparative Example 1

[0182] Cesium iodide and solar cells were prepared using the same method as in Example 1, except that the first additive was not added during the preparation of cesium iodide.

[0183] Table 1 below shows the performance parameters of the first additive and cesium iodide in Examples 1 to 8 and Comparative Example 1, and Table 2 below shows the photovoltaic parameters of the solar cells prepared in Examples 1 to 8 and Comparative Example 1.

[0184] Table 1

[0185]

[0186] In Table 1, " / " indicates that the symbol does not exist.

[0187] Table 2

[0188]

[0189] As can be seen from Tables 1 and 2, compared to Comparative Example 1 (where the first substance was absent in cesium iodide), the cesium iodide in Examples 1-8 did not deteriorate after 240 days of storage, reflecting that the introduction of the first substance into cesium iodide can improve its stability. Furthermore, the solar cells prepared using the cesium iodide in Examples 1-8 exhibit significantly improved photoelectric conversion efficiency, and the normalized efficiency of the solar cells after being placed in an atmospheric environment without light protection for 1000 hours also shows significant improvement, reflecting the high stability of the solar cell devices.

[0190] Example 9

[0191] Cesium iodide and solar cells were prepared using the same method as in Example 1, except that a second additive was added to the cesium salt solution during the preparation of cesium iodide. Specifically, 25 μL of acetic acid (purity 98%–99%) was measured and slowly added dropwise to the cesium carbonate solution, and stirred at 5°C for 20 min to obtain the cesium carbonate solution. The molar percentage of the second additive, acetic acid, in the cesium carbonate solution was 2.8%.

[0192] Examples 10-22

[0193] Cesium iodide and solar cells were prepared using the same method as in Example 9, except that the type or content of the second additive used was different, as specifically adjusted according to Table 3 below.

[0194] Table 3 below shows the performance parameters of the first additive, the second additive, and cesium iodide in Examples 9-21, and Table 4 below shows the photovoltaic parameters of the solar cells prepared in Examples 9-21.

[0195] Table 3

[0196]

[0197] Table 4

[0198]

[0199]

[0200] As can be seen from Tables 3 and 4, the cesium iodide in Examples 9-21 did not deteriorate after 240 days of storage. Furthermore, the solar cells prepared using the cesium iodide in Examples 9-21 exhibited further improved photoelectric conversion efficiency.

[0201] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A cesium iodide characterized in that, The first substance includes one or more of hypophosphite ion, phosphite ion, sulfite ion, bisulfite ion, tetrathionate ion, oxalate ion, and L-ascorbic acid.

2. The cesium iodide of claim 1, wherein, The first substance includes one or more of hypophosphite ion, phosphite ion, sulfite ion, bisulfite ion, tetrathionate ion, oxalate ion, and L-ascorbic acid.

3. The cesium iodide according to claim 1 or 2, characterized in that, The first substance includes hypophosphite ion and / or L-ascorbic acid.

4. The cesium iodide according to any one of claims 1 to 3, characterized in that, The first substance accounts for 0.01% to 1.5% of the molar ratio in the cesium iodide.

5. The cesium iodide according to any one of claims 1 to 4, characterized in that, The first substance accounts for 0.02% to 0.25% of the molar ratio in the cesium iodide.

6. The cesium iodide according to any one of claims 1 to 5, characterized in that, The cesium iodide further includes a second substance; the second substance includes an acid radical ion containing N element, O element, S element, P element, or halogen.

7. The cesium iodide of claim 6, wherein, The second substance includes one or more of nitrate ion, perchlorate ion, acetate ion, benzenesulfonate ion, formate ion, citrate ion, acrylic acid ion, salicylate ion, phosphate ion, bromide ion, and thiocyanate ion.

8. The cesium iodide according to claim 6 or 7, characterized in that, The second substance accounts for 0.001% to 0.45% of the molar ratio in the cesium iodide.

9. The cesium iodide according to any one of claims 6 to 8, characterized in that, The second substance accounts for 0.005% to 0.015% of the molar ratio in the cesium iodide.

10. A method for producing cesium iodide, characterized by, The method includes the following steps: S1, configuring an iodine-containing solution and a cesium salt solution, wherein the iodine-containing solution includes a first additive with reducing property; S2, mixing and stirring the iodine-containing solution and the cesium salt solution to obtain a cesium iodide solution; S3, purifying the cesium iodide solution to obtain cesium iodide.

11. The method of claim 10, wherein, The first additive includes one or more of sodium hypophosphite, sodium sulfite, sodium bisulfite, sodium sulfite, sulfurous acid, oxalic acid, sodium thiosulfate, and L-ascorbic acid.

12. The production method according to claim 10 or 11, characterized by, The first additive includes sodium hypophosphite and / or L-ascorbic acid.

13. The production method according to any one of claims 10 to 12, characterized by, The first additive accounts for 0.01% to 6% of the molar ratio in the iodine-containing solution.

14. The production method according to any one of claims 10 to 13, characterized by, The first additive accounts for 2% to 3% of the molar ratio in the iodine-containing solution.

15. The production method according to any one of claims 10 to 14, characterized by, Step S1 includes adding the first additive into an iodine-containing compound solution to obtain the iodine-containing solution. The iodine-containing compound includes hydroiodic acid and / or calcium iodide.

16. The method of claim 15, wherein, The iodine-containing compound includes hydroiodic acid.

17. The production method according to any one of claims 10 to 16, characterized by, Before step S2 is performed, the iodine-containing solution is placed in the dark at 2°C to 8°C for 4h to 6h.

18. The production method according to any one of claims 10 to 17, characterized by, Step S1 further includes dissolving a cesium salt in a solvent under inert gas to obtain the cesium salt solution.

19. The method of claim 18, wherein, The cesium salt includes one or more of cesium carbonate, cesium hydroxide, and cesium oxide.

20. The method of manufacturing according to claim 18 or 19, wherein, Step S1 further includes adding a second additive into the cesium salt solution and stirring at 2°C to 8°C for 0.5h to 1h.

21. The method of claim 20, wherein, The second additive includes an acid radical ion containing N element, O element, S element, P element, halogen ion, or pseudo-halogen ion.

22. The method of manufacturing according to claim 20 or 21, wherein, The second additive includes one or more of dilute nitric acid, perchloric acid, acetic acid, dodecylbenzenesulfonic acid, 4-chlorobenzenesulfonic acid, benzenesulfonic acid, formic acid, citric acid, acrylic acid, salicylic acid, thiocyanic acid, hydrobromic acid, and phosphoric acid.

23. The production method according to any one of claims 20 to 22, characterized by, The cesium salt solution accounts for 1% to 10% of the molar mass ratio of the second additive.

24. The production method according to any one of claims 20 to 23, characterized by, The cesium salt solution accounts for 2% to 3% of the molar mass ratio of the second additive.

25. The production method according to any one of claims 10 to 24, characterized by, In step S2, the stirring treatment is performed at 0°C to 10°C for 2h to 4h.

26. The production method according to any one of claims 10 to 25, wherein The purification treatment in step S3 includes an evaporation treatment, a filtration treatment, and a drying treatment.

27. The method of claim 26, wherein, The evaporation treatment includes evaporating and removing the solvent of the cesium iodide mixed solution to obtain unpurified cesium iodide.

28. The method of claim 27, wherein, The filtration treatment includes heating and dissolving the unpurified cesium iodide, and filtering to obtain a cesium iodide mother liquor, cooling treatment and filtering of the cesium iodide mother liquor to obtain treated cesium iodide, and cleaning and filtering of the treated cesium iodide with an alcohol solution to obtain purified cesium iodide.

29. The method of claim 28, wherein, The cooling treatment is cooled at a cooling rate of 5-12°C / min to 2-8°C.

30. The method of manufacturing according to claim 28 or 29, wherein, The drying treatment includes vacuum drying the purified cesium iodide at 50-80°C for 8-12h.

31. A solar cell, characterized by, The perovskite light-absorbing layer includes the cesium iodide of any one of claims 1-9, or the cesium iodide prepared according to the preparation method of any one of claims 10-30.

32. The solar cell of claim 31, wherein, The average grain size of the perovskite material in the perovskite light-absorbing layer is 200nm-2μm.

33. The solar cell according to claim 31 or 32, characterized in that, The photovoltaic component further includes a first transport layer and a second transport layer. The first transport layer is between the first electrode and the perovskite light-absorbing layer. The second transport layer is between the perovskite light-absorbing layer and the second electrode.

34. The solar cell of claim 33, wherein, The first transport layer is a hole transport layer, and the second transport layer is an electron transport layer; or the first transport layer is an electron transport layer, and the second transport layer is a hole transport layer.

35. A method for preparing a solar cell, characterized in that, The method further includes forming a first transport layer between the first electrode and the perovskite light-absorbing layer, and forming a second transport layer between the perovskite light-absorbing layer and the second electrode layer. The first transport layer is one of a hole transport layer and an electron transport layer, and the second transport layer is the other of the hole transport layer and the electron transport layer. The photovoltaic component includes the solar cell of any one of claims 31-34, or the solar cell prepared according to the preparation method of any one of claims 35-37. ​ 36. The method of claim 35, wherein the method is performed in a single step. ​ 37. The method of claim 36, wherein the method is performed in a single step. ​ 38. A photovoltaic module, characterized by, ​

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