Methods for preparing perovskite precursor materials, perovskite precursor solutions, and perovskite active layers.

Abstract

This invention provides a method for preparing a perovskite precursor material, comprising the following steps: mixing a lead halide with a low-polarity solvent; adding a coordination solvent in an amount equal to the molar number of the lead halide to form the perovskite precursor material. This method for preparing the perovskite precursor material reduces the number of preparation steps, saves on the amount of coordination solvent used, and is applicable to most coordination solvents. This invention also provides a method for preparing a perovskite precursor solution using the perovskite precursor material and a method for preparing a perovskite active layer, resulting in uniform grain size and good grain density in the perovskite active layer, and leading to perovskite optoelectronic devices with higher energy conversion efficiency and stability.

Description

Technical Field

[0001] The present invention relates to a method for preparing a perovskite precursor material, a method for preparing a perovskite precursor solution and a method for preparing a perovskite active layer of a perovskite photoelectric element. Prior Art

[0002] Perovskite optoelectronic materials have developed rapidly in recent years. Due to their good optical and electrical properties and their applicability to wet coating processes, they are used to manufacture low-cost and highly functional perovskite optoelectronic devices such as solar cells, light-emitting diodes, or light sensors.

[0003] The structure of existing perovskite photovoltaic devices consists, in order, of a substrate, a lower electrode, a lower carrier transport layer, a perovskite active layer, an upper carrier transport layer, an upper carrier modification layer, and a top electrode. One of the lower and upper carrier transport layers is a hole transport layer, and the other is an electron transport layer. The perovskite active layer is made from the perovskite precursor material PbX2(A), where Pb is lead and X is any of Cl (chlorine), Br (bromine), or I (iodine). A is a ligand capable of forming a coordination solvent with Pb, such as dimethyl sulfoxide (DMSO). Because DMSO is a liquid at room temperature and pressure, A is also called a coordination solvent. A typical example is PbX2(DMSO), which is a mixture of one equivalent of PbX2 and one equivalent of DMSO. However, PbX2 is a solid and DMSO is a liquid. Therefore, when preparing PbX2(DMSO), if equal amounts of PbX2 and DMSO are directly mixed and stirred, the viscosity will be too high during stirring, resulting in an uneven reaction. For example, when X is I, the typical phenomenon is the simultaneous presence of yellow PbI2, light yellow PbI2(DMSO), and white PbI2(DMSO)2.

[0004] To avoid the aforementioned uneven reaction, most existing methods use an excess of DMSO to ensure that PbI2 is completely dissolved in the DMSO. For example, Chinese Invention Patent Publication No. CN105679944A (hereinafter referred to as Document 1) uses 20 times the molar amount of DMSO as the molar amount of PbI2. It uses 5g of PbI2 (molecular weight 461.01 g / mol, 10.8 mmol) and 15ml of DMSO (density 1.104 g / cm3, molecular weight 78.13 g / mol, 212 mmol). However, this method will first produce PbI 2(DMSO) 2 instead of PbI 2(DMSO), so PbI 2(DMSO) 2 must be vacuumed or cleaned with IPA to produce PbI 2(DMSO). Lee et. al described such a method in ACS Appl. Mater. Interfaces 2020, 12, 7, 8233–8239) (hereinafter referred to as Reference 2). However, in addition to the waste of DMSO caused by using excessive DMSO, the preparation of PbI2(DMSO) using the above method also has the following disadvantages: 1. The preparation process is complicated, requiring a total of five steps to obtain the product PbI2(DMSO). These five steps include dissolving PbI2 in DMSO, precipitating PbI2(DMSO)2 in DMSO, filtering and drying the PbI2(DMSO)2 solid, washing the PbI2(DMSO)2 solid with IPA to produce PbI2(DMSO), and then filtering and drying to obtain the PbI2(DMSO)2 solid. 2. The applicable range of IPA usage is narrow. When washing the PbI2(DMSO)2 solid with IPA, the applicable molar ratio range of IPA to PbI2(DMSO)2 is narrow. If IPA is excessive, the x value of the perovskite precursor material PbI2(DMSO)x will be less than 1, that is, PbI2(DMSO)x will be less than 1. 2. The IPA / DMSO molar ratio is greater than 1. Insufficient IPA will cause the x value of the perovskite precursor material PbI2(DMSO)x to be greater than 1, that is, the PbI2 / DMSO molar ratio is less than 1. 3. The applicable amount of IPA is limited to specific solvent systems. If DMSO is replaced with other solvents such as N-methylpyrrolidone (NMP), tetramethylene sulfoxide (TMSO), or tetramethylene sulfone (TMS), the IPA dosage must be adjusted separately, which is inconvenient.Furthermore, due to the aforementioned shortcomings, the power conversion efficiency (PCE) of the perovskite photovoltaic device produced after preparing PbI2(DMSO) using the aforementioned method is also low and does not meet the expected effect.

[0005] References 1 and 2 first apply a perovskite precursor solution containing a perovskite precursor material to the carrier transport layer and dry it. A halide salt solution containing a halide salt is then applied and dried to form the perovskite active layer. However, this double coating method affects process efficiency and yield. Furthermore, the preparation method for the perovskite active layer can affect the density and uniformity of the grains in the perovskite active layer, thereby affecting the PCE of the perovskite photovoltaic device. One existing example utilizes a "single-step" method, where the halide salt and perovskite precursor material are directly dissolved in a bulk solvent (e.g., dimethylformamide, DMF) to form the perovskite precursor solution. The second existing example does not use a perovskite precursor material, but instead dissolves the halide salt, PbI2, and DMSO in a bulk solvent to form the perovskite precursor solution. Although these two examples only require one coating, the grain size in their perovskite active layer is uneven and the density is poor with a pinhole crystal morphology, resulting in the PCE of the perovskite photoelectric element being lower than expected.

[0006] Therefore, how to address the shortcomings of the aforementioned method for preparing the perovskite precursor material PbX2(A) to achieve more economical use of ligands (such as DMSO) and simpler preparation steps, as well as how to make the grain size in the perovskite active layer uniform and dense to obtain perovskite photoelectric devices with higher PCE, have become the current research goals. Summary of the Invention

[0007] Therefore, the first purpose of the present invention is to provide a method for preparing a perovskite precursor material that saves ligand usage and is simpler.

[0008] Based on the above-mentioned first object, the present invention provides a method for preparing a perovskite precursor material, which is suitable for preparing a perovskite precursor material. The chemical formula of the perovskite precursor material is PbX2(A), wherein Pb is lead, X is Cl, Br or I, and A is one selected from the group consisting of dimethyl sulfoxide (DMSO), N-methylpyrrolidone (1-Methyl-2-pyrrolidone, NMP), tetramethylene sulfoxide (TMSO) and tetramethylene sulfone (TMS). The preparation method of the perovskite precursor material comprises the following steps: 2) mixing with a low-polarity solvent and suspending the lead halide in the low-polarity solvent to form a suspension; adding a coordinating solvent in an amount equal to the molar number of the lead halide to the suspension so that the lead halide and the coordinating solvent form a liquid composition containing the perovskite precursor material, wherein the perovskite precursor material and the low-polarity solvent form the liquid composition, wherein the coordinating solvent is one selected from the group consisting of DMSO, NMP, TMSO and TMS.

[0009] More specifically, the polarity index of the low-polarity solvent is no greater than 3.

[0010] More specifically, the low polarity solvent is selected from one of the group consisting of n-hexane, n-heptane, toluene, xylene and chlorobenzene.

[0011] More specifically, when the coordinating solvent is added to the suspension, the temperature of the suspension is between 60° C. and 80° C. and maintained for at least two hours.

[0012] More specifically, the suspension is prepared by stirring the lead halide in the low-polarity solvent at a stirring speed of 150-300 RPM.

[0013] In one embodiment, the perovskite precursor material in the liquid composition is insoluble in the low-polarity solvent, and the method for preparing the perovskite precursor material further includes the following steps: removing the low-polarity solvent from the liquid composition to obtain the perovskite precursor material.

[0014] Furthermore, before the lead halide is mixed with the low-polarity solvent, the lead halide is contacted with isopropyl alcohol (IPA) and then the isopropyl alcohol is removed by filtration drying, nitrogen drying or vacuum drying.

[0015] More specifically, before the lead halide is mixed with the low-polarity solvent, the lead halide is mixed with the isopropyl alcohol and stirred, and then the isopropyl alcohol is removed by filtering and drying.

[0016] The effectiveness of the method for preparing the perovskite precursor material of the present invention lies in: the steps for obtaining the perovskite precursor material through the method of the present invention are simple. Compared with the five steps in the previous technical documents 1 and 2, the present invention reduces the steps to two to three steps to obtain the perovskite precursor material, thus being more conducive to large-scale production. In addition, the method for preparing the perovskite precursor material of the present invention saves the amount of ligand (coordinating solvent) used and is applicable to most coordinating solvents.

[0017] The second object of the present invention is to provide a method for preparing a perovskite active layer in which the grains are uniform in size and have good density.

[0018] Based on the above-mentioned second objective, the present invention first provides a method for preparing a perovskite precursor solution, which comprises the following steps: dissolving a halide salt in a host solvent to form a halide salt solution; then, adding the perovskite precursor material to the halide salt solution in an amount between 0.9 and 1.1 times the molar number of the halide salt to form a perovskite precursor solution, wherein the concentrations of the halide salt and the perovskite precursor material in the perovskite precursor solution are respectively between 0.5M and 1.6M.

[0019] More specifically, the halide salt is at least one selected from the group consisting of cesium iodide (CsI), cesium bromide (CsBr), cesium chloride (CsCl), methylammonium iodide (MAI), methylammonium bromide (MABr), methylammonium chloride (MACl), formamidinium iodide (FAI), formamidinium bromide (FABr), and formamidinium chloride (FACl), or a combination thereof.

[0020] More specifically, the main solvent is selected from at least one of the group consisting of dimethylformamide (DMF), dimethylacetamide (DMAc) and gamma-butyrolactone (GBL), or a combination thereof.

[0021] In one embodiment, the concentrations of the halide salt and the perovskite precursor material in the perovskite precursor solution are respectively 1.45M.

[0022] In one embodiment, the perovskite precursor material is added to the halide salt solution in an amount of 1.015 times the molar number of the halide salt to form the perovskite precursor solution.

[0023] Based on the above second object, the present invention then provides a method for preparing a perovskite active layer, which is suitable for preparing a perovskite active layer in a perovskite photoelectric element. The method for preparing the perovskite active layer is subsequent to the method for preparing the perovskite precursor solution, and then the following steps are performed in sequence: the perovskite precursor solution is coated on a carrier transport layer in a coating manner to form a perovskite coating layer on the upper surface of the carrier transport layer, the perovskite coating layer comprising the halide salt, the perovskite precursor material and the main solvent; the main solvent is removed from the perovskite coating layer in a drying manner to form a perovskite precursor layer, the perovskite precursor layer comprising the halide salt and the perovskite precursor material; the perovskite precursor material in the perovskite precursor layer is deliganded by a ligand removal method to form the perovskite active layer from the perovskite precursor layer.

[0024] More specifically, the coating method includes but is not limited to any one of spin coating, doctor blade coating, rod coating, slit coating, spray coating, inkjet printing, and screen printing.

[0025] More specifically, the drying method includes but is not limited to any one of an anti-solvent method, an air knife method, and a vacuum method.

[0026] In one embodiment, the vacuum decompression method refers to placing the perovskite coating layer in a cylinder and allowing the air pressure in the cylinder to reach a vacuum rate of less than 1 Torr within 20 seconds.

[0027] In one embodiment, the air pressure in the cylinder is maintained at an air pressure environment of less than 1 Torr for more than 30 seconds.

[0028] More specifically, the ligand removal method is a heating method, which includes but is not limited to any one of a baking tray heating method, an oven heating method, a microwave heating method, and a plasma heating method.

[0029] In one embodiment, the heating temperature of the baking tray heating method or the oven heating method is between 50°C and 350°C.

[0030] In one embodiment, when the halide salt is at least one selected from the group consisting of methylammonium iodide (MAI), methylammonium bromide (MABr), methylammonium chloride (MACl), formamidinium iodide (FAI), formamidinium bromide (FABr), and formamidinium chloride (FACl), or a combination thereof, the heating temperature of the hotplate heating method or the oven heating method is between 50° C. and 200° C.

[0031] The effectiveness of the method for preparing the perovskite active layer of the present invention lies in that, compared to the "single-step" method of the aforementioned prior art in which a halide salt and a perovskite precursor material are directly dissolved together in a main solvent, the method for preparing the perovskite precursor solution of the present invention uses a "two-step method" of first preparing a halide salt solution and then adding the perovskite precursor material to prepare the perovskite precursor solution. This allows the perovskite precursor material to obtain optimal stability in the perovskite precursor solution, resulting in uniform grain size and good density between grains in the perovskite active layer, ultimately improving the power conversion efficiency (PCE) and stability of the perovskite photoelectric device.

[0032] The perovskite photovoltaic element of the present invention comprises a substrate, a lower electrode, a lower carrier transport layer, the perovskite active layer, an upper carrier transport layer, an upper carrier modification layer, and a top electrode. The lower electrode is laminated on the substrate, the lower carrier transport layer is laminated on the lower electrode, the perovskite active layer is laminated on the lower carrier transport layer, the upper carrier transport layer is laminated on the perovskite active layer, the upper carrier modification layer is laminated on the upper carrier transport layer, and the top electrode is laminated on the upper carrier modification layer. One of the lower carrier transport layer and the upper carrier transport layer is a hole transport layer, and the other is an electron transport layer. Simple diagram description

[0033] Other features and effects of the present invention will be clearly presented in the embodiments with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional schematic diagram illustrating the structure of the perovskite photoelectric element of the present invention; Figure 2 is a schematic flow chart illustrating a method for preparing a perovskite precursor material according to the present invention; Figure 3 is a schematic flow chart illustrating a method for preparing a perovskite active layer according to the present invention; FIG4 is a scanning electron microscope photograph illustrating the crystal morphology of Examples 1-2 and Comparative Examples 1-2; and FIG5 is a graph illustrating the stability results of the perovskite photoelectric device of Application Example 3 and Comparative Application Example 2 under continuous illumination. Implementation Method

[0034] <Perovskite Photovoltaic Device Structure>

[0035] Referring to FIG. 1 , the structure of the perovskite photovoltaic device of the present invention includes a substrate A, a lower electrode B, a lower carrier transport layer C, a perovskite active layer D, an upper carrier transport layer E, an upper carrier modification layer F, and a top electrode G. The lower electrode B is laminated on the substrate A. The lower carrier transport layer C is laminated on the lower electrode B. The perovskite active layer D is laminated on the lower carrier transport layer C. The upper carrier transport layer E is laminated on the perovskite active layer D. The upper carrier modification layer F is laminated on the upper carrier transport layer E. The top electrode G is laminated on the upper carrier modification layer F. One of the lower carrier transport layer C and the upper carrier transport layer E is a hole transport layer, and the other is an electron transport layer; wherein the perovskite active layer D is first prepared by a method for preparing a perovskite precursor material to prepare a perovskite precursor material, then the perovskite precursor material is used to prepare a perovskite precursor solution by a method for preparing a perovskite precursor solution, and then the perovskite precursor solution is used to prepare the perovskite active layer D by a method for preparing a perovskite active layer.

[0036] [Preparing a perovskite precursor material using a method for preparing a perovskite precursor material]

[0037] The general chemical formula of the perovskite precursor material is PbX2(A), wherein Pb is lead, X is Cl, Br or I, and A is one selected from the group consisting of dimethyl sulfoxide (DMSO), N-methylpyrrolidone (1-Methyl-2-pyrrolidone, NMP), tetramethylene sulfoxide (TMSO) and tetramethylene sulfone (TMS). Please refer to Figure 2. The preparation method of the perovskite precursor material comprises the following steps: preparing a lead halide (PbX2) 2) mixing with a low-polarity solvent and suspending the lead halide in the low-polarity solvent to form a suspension; adding a coordinating solvent in an amount equal to the molar number of the lead halide to the suspension so that the lead halide and the coordinating solvent form a liquid composition containing the perovskite precursor material, wherein the perovskite precursor material and the low-polarity solvent form the liquid composition, wherein the coordinating solvent is selected from the group consisting of DMSO, NMP, TMSO, and TMS. Preferably, the method for preparing the perovskite precursor material further comprises the following steps: removing the low-polarity solvent from the liquid composition to obtain the perovskite precursor material. Furthermore, before mixing the lead halide with the low-polarity solvent, the lead halide is contacted with isopropyl alcohol (IPA) and then the isopropyl alcohol is removed.

[0038] <Preparation Example 1>

[0039] 5 g of PbI2 (10.85 mmol) was added to a vessel containing 35 mL of n-heptane (polarity index 0.2) and stirred with a high-speed mechanical stirrer at a stirring speed of 150-300 RPM to form a suspension. 0.848 g of DMSO (10.85 mmol) as a coordination solvent was then added to the suspension in the vessel containing PbI2 and n-heptane and stirred at 60°C for 2 hours to form a liquid composition containing PbI2(DMSO). The liquid composition containing fully coordinated PbI2(DMSO) and n-heptane was transferred to a filtration vessel, filtered, and dried with nitrogen purge to remove the n-heptane, obtaining 4.2 g of PbI2(DMSO) as a solid product, perovskite precursor material 1.

[0040] <Preparation Example 2>

[0041] 10 g of PbI2 (21.69 mmol) was added to a vessel containing 70 mL of IPA and stirred with a high-speed mechanical stirrer for 2 hours at a stirring speed of 150-300 RPM. The PbI2 and IPA were then transferred to a filtration vessel for filtration to remove the IPA, obtaining approximately 10 g of PbI2 washed with IPA. The 10 g of PbI2 washed with IPA (21.69 mmol) was added to a vessel containing 70 mL of n-heptane and stirred with a high-speed mechanical stirrer at a stirring speed of 150-300 RPM to form a suspension. 1.7 g of DMSO (21.7 mmol) was then added to the suspension in the vessel containing PbI2 and n-heptane and stirred at 60°C for 2 hours to form a liquid composition containing PbI2 (DMSO). The fully coordinated PbI2 was added to a filtration vessel containing 10 g of PbI2 (21.69 mmol). The liquid composition of PbI 2 (DMSO) and n-heptane was transferred to a filter tank for filtration and dried with nitrogen to remove the n-heptane, thereby obtaining 9.1 g of PbI 2 (DMSO), a solid product of the perovskite precursor material 2.

[0042] Preparation Example 2 differs from Preparation Example 1 in that, in Preparation Example 2, the isopropyl alcohol is removed after the lead halide is contacted with the isopropyl alcohol before mixing the lead halide with the low-polarity solvent. More specifically, in Preparation Example 2, the isopropyl alcohol is removed by filtration and drying after the lead halide and the isopropyl alcohol are mixed and stirred before mixing the lead halide with the low-polarity solvent.

[0043] [Perovskite precursor material prepared by the preparation methods of the aforementioned documents 1 and 2]

[0044] <Comparative Preparation Example 1>

[0045] 10 g of PbI 2 (21.69 mmol) was dissolved in 30 mL of DMSO (424 mmol) and stirred at 60°C overnight. After cooling, the insoluble matter was filtered with filter paper and 70 mL of toluene was slowly added dropwise to the reaction flask for precipitation. The precipitate was filtered and dried at room temperature for at least 3 hours to obtain 9.2 g of PbI 2 (DMSO) 2. 9.2 g of PbI 2 (DMSO) 2 was added to 45 mL of IPA with continuous stirring and continued stirring for 3 hours. After filtering to obtain the crude product, it was dried in a vacuum at room temperature for at least 20 hours to obtain 8.2 g of PbI 2 (DMSO) as a solid product, perovskite precursor material 3.

[0046] Preparation Comparative Example 1 is a five-step process for preparing the perovskite precursor material according to prior art documents 1 and 2, and the amount of DMSO is approximately 20 times the amount of PbI2. Preparation Examples 1 and 2 are the present invention, which reduces the process to two to three steps to obtain the perovskite precursor material, and the amount of DMSO is only approximately equal to the amount of PbI2, without requiring an excess of 20 times.

[0047] [Preparing a perovskite precursor solution by a method for preparing a perovskite precursor solution]

[0048] Referring to FIG. 3 , the method for preparing a perovskite precursor solution comprises the following steps: dissolving a halide salt in a host solvent to form a halide salt solution; then, adding a perovskite precursor material to the halide salt solution in an amount ranging from 0.9 to 1.1 times the molar ratio of the halide salt to form a perovskite precursor solution. Preferably, the concentrations of the halide salt and the perovskite precursor material in the perovskite precursor solution are each between 0.5 M and 1.6 M. The halide salt is selected from the group consisting of cesium iodide (CsI), cesium bromide (CsBr), cesium chloride (CsCl), methylamine iodide (MAI), methylamine bromide (MABr), methylamine chloride (MACl), formamidine iodide (FAI), formamidine bromide (FABr), and formamidine chloride (FACl), or a combination thereof. The main solvent is at least one selected from the group consisting of dimethylformamide (DMF), dimethylacetamide (DMAc) and gamma-butyrolactone (GBL) or a combination thereof.

[0049] [Perovskite active layer prepared by the method for preparing the perovskite active layer]

[0050] Referring again to FIG. 3 , the method for preparing the perovskite active layer follows the method for preparing the perovskite precursor solution, and then sequentially performs the following steps: applying the perovskite precursor solution to a carrier transport layer by a coating method to form a perovskite coating layer on the upper surface of the carrier transport layer, wherein the perovskite coating layer comprises the halide salt, the perovskite precursor material, and the bulk solvent; drying the perovskite coating layer to remove the bulk solvent to form a perovskite precursor layer, wherein the perovskite precursor layer comprises the halide salt and the perovskite precursor material; and removing the coordination solvent from the perovskite precursor material in the perovskite precursor layer by a deliganding method to form the perovskite active layer. The drying method includes, but is not limited to, any one of an anti-solvent method, an air knife method, and a vacuum method. The vacuum decompression method refers to placing the perovskite coating layer in a cylinder and causing the air pressure in the cylinder to reach a vacuum rate of less than 1 Torr within 20 seconds, and the air pressure in the cylinder is maintained at an air pressure environment of less than 1 Torr for more than 30 seconds.

[0051] <Example 1>

[0052] Prepare perovskite precursor solution 1: Dissolve CsI (0.25 mmol) and FAI (1.2 mmol) in 1 mL of DMF to form a halide salt solution. Add perovskite precursor material 1 (1.45 mmol) to the halide salt solution containing CsI and FAI in DMF while stirring. Stir for 30 minutes to form perovskite precursor solution 1. The concentrations of the halide salt and the perovskite precursor material in perovskite precursor solution 1 in Example 1 were each 1.45 M.

[0053] Preparation of perovskite active layer 1: Spin-coating a perovskite precursor solution 1 on the lower carrier transport layer of a substrate having a lower carrier transport layer and a lower electrode thereon to form a perovskite coating layer; placing the perovskite coating layer in a cylinder and removing DMF by vacuum decompression to form a perovskite precursor layer, wherein the vacuum decompression method refers to causing the air pressure in the cylinder to reach a vacuum rate of less than 1 Torr within 20 seconds and maintaining the air pressure in the cylinder at a pressure environment of less than 1 Torr for 30 seconds; heating the pre-dried perovskite precursor layer on a baking tray at 100°C for 30 minutes to obtain a perovskite active layer 1 having a thickness of approximately 400 nm.

[0054] <Example 2>

[0055] Preparation of perovskite precursor solution 2: Dissolve CsI (0.25 mmol) and FAI (1.2 mmol) in 1 mL of DMF to form a halide solution. Add perovskite precursor material 2 (1.45 mmol) to the halide solution containing CsI and FAI in DMF while stirring for 30 minutes to form perovskite precursor solution 2.

[0056] Preparation of perovskite active layer 2: Spin-coating a perovskite precursor solution 2 on the lower carrier transport layer of a substrate having a lower carrier transport layer and a lower electrode thereon to form a perovskite coating layer; placing the perovskite coating layer in a cylinder and removing DMF by vacuum decompression to form a perovskite precursor layer, wherein the vacuum decompression method refers to causing the air pressure in the cylinder to reach a vacuum rate of less than 1 Torr within 20 seconds and maintaining the air pressure in the cylinder at a pressure environment of less than 1 Torr for 30 seconds; heating the pre-dried perovskite precursor layer on a baking tray at 100°C for 30 minutes to obtain a perovskite active layer 2 having a thickness of approximately 400 nm.

[0057] <Example 3>

[0058] Preparation of perovskite precursor solution 3: Dissolve CsI (0.25 mmol) and FAI (1.2 mmol) in 1 mL of DMF to form a halide solution. Add perovskite precursor material 2 (1.47 mmol) to the halide solution containing CsI and FAI in DMF while stirring continuously for 30 minutes to form perovskite precursor solution 3.

[0059] Preparation of perovskite active layer 3: Spin-coating a perovskite precursor solution 3 on the lower carrier transport layer of a substrate having a lower carrier transport layer and a lower electrode thereon to form a perovskite coating layer; placing the perovskite coating layer in a cylinder and removing DMF by vacuum decompression to form a perovskite precursor layer, wherein the vacuum decompression method refers to causing the air pressure in the cylinder to reach a vacuum rate of less than 1 Torr within 20 seconds and maintaining the air pressure in the cylinder at a pressure environment of less than 1 Torr for 30 seconds; heating the pre-dried perovskite precursor layer on a baking tray at 100°C for 30 minutes to obtain a perovskite active layer 3 having a thickness of approximately 400 nm.

[0060] The difference between Example 3 and Example 2 is that the molar number of the perovskite precursor material in Example 3 is 1.015 times the molar number of the halide salt, while in Example 2 it is the same amount.

[0061] <Example 4>

[0062] Preparation of perovskite precursor solution 2: Same as Example 2.

[0063] Preparation of perovskite active layer 4: Perovskite precursor solution 2 is spin-coated onto the lower carrier transport layer of a substrate having a lower carrier transport layer and a lower electrode laminated thereon to form a perovskite coating layer. The perovskite coating layer is placed in a vat and DMF is removed by vacuum decompression to form a perovskite precursor layer. Vacuum decompression refers to the process of reducing the pressure in the vat to a vacuum rate of less than 1 Torr within 20 seconds. The pre-dried perovskite precursor layer is heated on a hotplate at 100°C for 30 minutes to obtain a perovskite active layer 4 with a thickness of approximately 400 nm.

[0064] The difference between Example 4 and Example 2 is that Example 4 does not maintain the air pressure in the cylinder at an air pressure environment of less than 1 Torr for 30 seconds, while Example 2 does maintain the air pressure in the cylinder at an air pressure environment of less than 1 Torr for 30 seconds.

[0065] <Comparative Example 1>

[0066] Preparation of perovskite precursor solution 4: CsI (0.25 mmol), FAI (1.2 mmol) and perovskite precursor material 2 (1.45 mmol) prepared in Preparation Example 2 were dissolved in 1 mL of DMF and stirred for 30 minutes to form perovskite precursor solution 4.

[0067] Preparation of perovskite active layer 5: Spin-coating a perovskite precursor solution 4 onto the lower carrier transport layer of a substrate having a lower carrier transport layer and a lower electrode thereon to form a perovskite coating layer; placing the perovskite coating layer in a cylinder and removing DMF by vacuum decompression to form a perovskite precursor layer, wherein the vacuum decompression method refers to causing the air pressure in the cylinder to reach a vacuum rate of less than 1 Torr within 20 seconds and maintaining the air pressure in the cylinder at a pressure environment of less than 1 Torr for 30 seconds; heating the pre-dried perovskite precursor layer on a baking tray at 100°C for 30 minutes to obtain a perovskite active layer 5 having a thickness of approximately 400 nm.

[0068] <Comparative Example 2>

[0069] Preparation of perovskite precursor solution 5: CsI (0.25 mmol), FAI (1.2 mmol) and perovskite precursor material 3 (1.45 mmol) prepared in Comparative Example 1 were dissolved in 1 mL of DMF and stirred for 30 minutes to form perovskite precursor solution 5.

[0070] Preparation of perovskite active layer 6: Spin-coating a perovskite precursor solution 5 onto the lower carrier transport layer of a substrate having a lower carrier transport layer and a lower electrode thereon to form a perovskite coating layer; placing the perovskite coating layer in a cylinder and removing DMF by vacuum decompression to form a perovskite precursor layer, wherein the vacuum decompression method is performed by causing the air pressure in the cylinder to reach a vacuum rate of less than 1 Torr within 20 seconds; heating the pre-dried perovskite precursor layer on a baking tray at 100°C for 30 minutes to obtain a perovskite active layer 6 having a thickness of approximately 400 nm.

[0071] <Crystalline Morphology of Perovskite Active Layers in Examples and Comparative Examples>

[0072] Examples 1-4 utilize a "two-step" method, according to the present invention, to prepare the perovskite precursor solution, first preparing the halide salt solution and then adding the perovskite precursor material. Comparative Examples 1 and 2, however, utilize a "single-step" method, as previously described, in which the halide salt and perovskite precursor material are directly dissolved in a bulk solvent. Scanning electron micrographs of the perovskite crystal layers of Examples 1 and 2 and Comparative Examples 1 and 2 (Figure 4) show that the perovskite precursor materials 1 and 2 and perovskite active layers 1 and 2 of Examples 1-2 of the present invention exhibit superior crystal uniformity, improved grain size uniformity, and improved grain-to-grain density compared to the perovskite active layers 5 and 6 of Comparative Examples 1 and 2. Therefore, the present invention's methods for preparing the perovskite precursor solution and perovskite active layer demonstrate significant efficacy compared to prior art methods and can mitigate the adverse effects of grain boundary defects on the power conversion efficiency (PCE) and stability of subsequent perovskite photovoltaic devices.

[0073] <Preparation of perovskite photoelectric devices>

[0074] The perovskite photovoltaic devices of Application Examples 1-5 and Comparative Application Examples 1-2 were prepared according to the perovskite active layer shown in Table 1 below. Table 1 Perovskite photoelectric device number Corresponding Examples or Comparative Examples The corresponding perovskite active layer number Implementation Example 1 Example 1 Perovskite active layer 1 Implementation Example 2 Example 2 Perovskite active layer 2 Implementation Application Example 3 Example 3 Perovskite active layer 3 Implementation Example 4 Example 4 Perovskite active layer 4 Comparative Application Example 1 Comparative Example 1 Perovskite active layer 5 Comparative Application Example 2 Comparative Example 2 Perovskite active layer 6

[0075] An indium tin oxide (ITO) glass substrate (12 Ω / □) was cleaned using detergent, deionized water, acetone, and isopropyl alcohol, followed by ultrasonic cleaning for 15 minutes. The surface was then cleaned in a UV ozone cleaner for 30 minutes. The glass substrate was referred to as substrate A, and the indium tin oxide (ITO) was referred to as bottom electrode B.

[0076] The hole transport material PTAA (poly(triaryl amine)) was mixed with the solvent toluene to form a solution with a solid content of 1.5 wt%. This solution was coated onto an ITO glass substrate and baked at 100-120°C for 10-30 minutes to form a hole transport layer C with a thickness of approximately 20 nm.

[0077] The substrate covered with the carrier transport layer C was first subjected to surface treatment in a UV ozone cleaner for 5 minutes, and then the corresponding perovskite active layer was prepared according to the above-mentioned Examples 1-4 and Comparative Examples 1-2 to form a perovskite active layer D.

[0078] PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) was mixed with chlorobenzene to form a solution with a solid content of 2.5 wt%. This solution was applied to the perovskite crystal layer and baked at 80-100°C for 10 minutes to form the upper carrier transport layer E with a thickness of approximately 50 nm.

[0079] An AZO (aluminum-doped zinc oxide) nanoparticle suspension with a solid content of 2.5 wt% was coated on the PCBM and baked at 120-140°C for 6 minutes to form an upper carrier modification layer F with a thickness of approximately 30 nm.

[0080] The sample obtained above was first placed in a vacuum chamber, and then silver metal was evaporated at 1.0x10-6Torr to form the upper electrode G with a thickness of about 100 nm, thereby obtaining a perovskite photoelectric element.

[0081] [<] [Energy conversion efficiency of perovskite photovoltaic devices] [(PCE)] [analyze] [>]

[0082] The active area of ​​the perovskite photovoltaic device was defined by a metal mask as 0.04 cm². A Keithley 2400 power supply, controlled by a LabView program, was used to measure the electrical properties of the perovskite photovoltaic device under 100 mW / cm² AM1.5G simulated sunlight (SAN-EI XES-40S3). The data were recorded using a computer program to obtain current-voltage characteristic parameters.

[0083] The open circuit voltage (V oc), short-circuit current (J sc), fill factor (FF), and power conversion efficiency (PCE) of the perovskite photovoltaic devices of Examples 1-4 and Comparative Examples 1-2 obtained through the aforementioned electrical analysis results are summarized in Table 2 below. Table 2 Perovskite photoelectric device number Corresponding Examples or Comparative Examples Corresponding perovskite active layer number Method for preparing perovskite precursor solution V oc (V) J sc(Ma / cm -2) FF (%) PCE (%) Implementation Example 1 Example 1 Perovskite active layer 1 Two-step method 1.004 19.07 78.82 15.09 Implementation Example 2 Example 2 Perovskite active layer 2 Two-step method 1.040 20.50 73.89 15.76 Implementation Application Example 3 Example 3 Perovskite active layer 3 Two-step method 1.028 20.79 76.91 16.83 Implementation Example 4 Example 4 Perovskite active layer 4 Two-step method 1.052 19.42 75.20 15.36 Comparative Application Example 1 Comparative Example 1 Perovskite active layer 5 Single step 1.016 20.02 70.95 14.43 Comparative Application Example 2 Comparative Example 2 Perovskite active layer 6 Single step 0.980 19.93 73.08 14.28

[0084] Table 2 shows that the perovskite precursor solution preparation methods corresponding to Examples 1-4 utilize the present invention's "two-step method" (all with PCEs exceeding 15%). Compared to the prior art "single-step" method used in Examples 1-2 (all with PCEs below 15%), Examples 1-4 clearly exhibit higher PCEs using the present invention's "two-step method." Examples 2 and 4 (PCEs of 15.76% and 15.35%, respectively) both incorporate the lead halide and isopropyl alcohol into the solution before mixing them with the low-polarity solvent, followed by filtration and drying to remove the isopropyl alcohol. However, Example 1 (PCE of 15.09%) omitted this step, resulting in a relatively lower PCE. Example 2 (PCE of 15.76%) maintained the pressure in the chamber at less than 1 Torr for 30 seconds, while Example 4 (PCE of 15.35%) omitted this step, resulting in a relatively lower PCE. The difference between Example 3 (PCE of 16.83%) and Example 2 (PCE of 15.76%) is that the molar amount of the perovskite precursor material in Example 3 is 1.015 times the molar amount of the halide salt, while in Example 2, it is the same amount. Therefore, Example 3 has a higher PCE, making Example 3 the best example. In addition, Comparative Example 2 (PCE of 14.28%) uses five steps to prepare the perovskite precursor material, as described in prior art documents 1 and 2, and the amount of DMSO is approximately 20 times the amount of PbI2. Comparative Example 1 (PCE of 14.43%) reduces the process to two to three steps to obtain the perovskite precursor material, and the amount of DMSO is only approximately the same as the amount of PbI2, rather than requiring a 20-fold excess. Furthermore, the PCE is higher than that of Comparative Example 2.

[0085] [<] [Stability test of perovskite photoelectrics] [>]

[0086] The perovskite photoelectric elements of Application Example 3 and Comparative Application Example 2 were continuously illuminated to simulate actual application conditions. The test results are shown in FIG5 .

[0087] As can be seen from Figure 5, compared with Comparative Application Example 2, the perovskite photoelectric element (Implementation Application Example 3) produced by the preparation method of the perovskite precursor material, the preparation method of the perovskite precursor solution and the preparation method of the perovskite active layer of the present invention has a more stable power conversion efficiency (PCE). This is because the perovskite active layer prepared according to the method disclosed in the present invention has better crystallization uniformity and improved grain size uniformity, thereby reducing the adverse effects of grain boundary defects on the perovskite photoelectric element and improving PCE.

[0088] In summary, the method of the present invention simplifies the steps for obtaining the perovskite precursor material. Compared to the five steps in prior art documents 1 and 2, the present invention reduces the process to just two or three steps to obtain the perovskite precursor material, making it more suitable for large-scale production. Furthermore, the method of preparing the perovskite precursor material of the present invention saves on the amount of ligands (coordinating solvents) used and is applicable to a wide range of coordinating solvents. Furthermore, compared to the prior art method of directly dissolving the halide salt and the perovskite precursor material in a bulk solvent in a "single step," the method of preparing the perovskite precursor solution of the present invention utilizes a "two-step approach" of first preparing the halide salt solution and then adding the perovskite precursor material. This ensures that the perovskite precursor material achieves optimal stability within the perovskite precursor solution, resulting in uniform grain size and excellent grain-to-grain density in the perovskite active layer, ultimately improving the power conversion efficiency (PCE) and stability of the perovskite photovoltaic device.

[0089] However, the above is merely an embodiment of the present invention and should not be used to limit the scope of implementation of the present invention. All simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the patent specification are still within the scope of the patent of the present invention.

[0090] A:Substrate B: Bottom electrode C: Download sub-transport layer D: Perovskite active layer E: Upload sub-transport layer F: Upload sub-modification layer G: Upper electrode

Claims

1. A method for preparing a perovskite precursor material, applicable to the preparation of a perovskite precursor material having the general chemical formula PbX2(A), wherein Pb is lead, X is Cl, Br or I, and A is selected from dimethyl sulfoxide (DMSO), 1-methyl-2-pyrrolidone (NMP), tetramethylene sulfoxide (TMSO) and tetramethylene... The method for preparing the perovskite precursor material comprises the following steps: mixing a lead halide with a low-polarity solvent and suspending the lead halide in the low-polarity solvent to form a suspension; adding a coordination solvent in an amount equal to the molar number of the lead halide to the suspension so that the lead halide and the coordination solvent form a liquid composition containing the perovskite precursor material, wherein the perovskite precursor material and the low-polarity solvent form the liquid composition, and the coordination solvent is selected from the group consisting of DMSO, NMP, TMSO and TMS.

2. The method for preparing the perovskite precursor material as described in claim 1, wherein, The polarity index of this low-polarity solvent is no greater than 3.

3. The method for preparing the perovskite precursor material as described in claim 2, wherein, The low-polarity solvent is selected from one of the groups consisting of n-hexane, n-heptane, toluene, xylene, and chlorobenzene.

4. The method for preparing the perovskite precursor material as described in claim 1, wherein, The preparation method of the perovskite precursor material further includes the following steps: after removing the low-polarity solvent from the liquid composition, the perovskite precursor material is obtained.

5. The method for preparing the perovskite precursor material as described in claim 1, wherein, Before mixing the lead halide with the low-polarity solvent, the lead halide is contacted with isopropanol and then the isopropanol is removed.

6. A method for preparing a perovskite precursor solution, the method comprising the following steps: dissolving a halide salt in a main solvent to form a halide salt solution; then adding a perovskite precursor material to the halide salt solution in an amount between 0.9 and 1.1 times the molar number of the halide salt to form a perovskite precursor solution, wherein the concentrations of the halide salt and the perovskite precursor material in the perovskite precursor solution are between 0.5 M and 1.6 M, respectively.

7. The method for preparing the perovskite precursor solution as described in claim 6, wherein, The halide is selected from at least one or a combination of the group consisting of cesium iodide (CsI), cesium bromide (CsBr), cesium chloride (CsCl), methylammonium iodide (MAI), methylammonium bromide (MABr), methylammonium chloride (MACl), formamidinium iodide (FAI), formamidinium bromide (FABr), and formamidinium chloride (FACl), and / or the main solvent is selected from at least one or a combination of the group consisting of dimethylformamide (DMF), dimethylacetamide (DMAc), and gamma-butyrolactone (GBL).

8. A method for preparing a perovskite active layer, applicable to the preparation of a perovskite active layer in a perovskite optoelectronic device, wherein the method for preparing the perovskite active layer is followed by the method for preparing a perovskite precursor solution as described in any one of claims 6 to 7, and then the following steps are performed sequentially: coating the perovskite precursor solution onto a downloader transport layer in a coating manner to form a perovskite coating layer on the upper surface of the downloader transport layer, the perovskite coating layer comprising the halide, the perovskite precursor material and the main solvent; removing the main solvent from the perovskite coating layer by a drying method to form a perovskite precursor layer, the perovskite precursor layer comprising the halide and the perovskite precursor material; removing the coordination solvent from the perovskite precursor material in the perovskite precursor layer by a coordination group removal method, so that the perovskite precursor layer forms the perovskite active layer.

9. The method for preparing the perovskite active layer as described in claim 8, wherein, The coating method can be spin coating, doctor blade coating, bar coating, slot coating, spray coating, inkjet printing, or screen printing. The drying method can be anti-solvent, air knife, or vacuum drying. The ligand removal method is a heating method.

10. The method for preparing the perovskite active layer as described in claim 9, wherein, The drying method is a vacuum decompression method, which refers to placing the perovskite coating layer in a cylinder and making the air pressure in the cylinder reach a vacuum rate of less than 1 Torr within 20 seconds, and maintaining the air pressure in the cylinder at a pressure of less than 1 Torr for more than 30 seconds.

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