A perovskite layer and preparation method thereof, and a perovskite solar cell

Abstract

Aiming at the problem of ionic defects commonly existing in the existing perovskite thin films, which reduces the photoelectric conversion efficiency of solar cells, the present application provides a perovskite layer, a preparation method thereof, and a perovskite solar cell; the perovskite layer includes an imidazo[2,1-b]thiazole derivative additive shown in Structural Formula 1, #imgabs0#; wherein, R1 is selected from one of #imgabs1#, #imgabs2#, #imgabs3#, and alkyl; R2, R3, and R4 are each independently selected from one or more of H, alkoxy, and alkyl substituted or unsubstituted by halogen. The perovskite layer provided by the present application contains a variety of Lewis base groups, which can coordinate with Pb in the perovskite precursor 2+ to undergo Lewis acid-base coordination in the solution state, effectively hindering the coordination crystallization of I ‑ with Pb 2+ , reducing the crystallization rate of perovskite, improving the crystallinity of the perovskite layer, reducing ionic defects, thereby inhibiting the non-radiative recombination process and enhancing the photoelectric conversion efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite solar cells, and in particular to a perovskite layer, a preparation method thereof, and a perovskite solar cell. Background Art

[0002] Perovskite solar cells, as a new type of photovoltaic device, have attracted much attention due to their excellent photoelectric conversion efficiency and low production cost. The core of perovskite solar cells lies in perovskite semiconductor materials, which can generate excitons through the photoelectric effect when irradiated with light and quickly separate into electrons and holes. The reverse migration of these charge carriers within the device generates current and voltage. The existing perovskite solar cell structure generally consists of a conductive base layer, an electron transport layer, a perovskite layer, a hole transport layer, and a metal electrode layer.

[0003] The crystallization of the perovskite layer, i.e., the perovskite thin film, in perovskite solar cells is often uncontrollable and affected by many factors. Due to the ionic properties of metal halide perovskites and their low defect formation energy, various defects inevitably occur on the surface and grain boundaries of polycrystalline thin films, resulting in serious non-radiative recombination or ion migration, and reducing the photoelectric conversion efficiency of the battery; in addition, defects such as grain boundaries and dangling bonds may become permeation channels for water molecules and oxygen, further affecting the stability of the battery. Summary of the Invention

[0004] Aiming at the problem of ionic defects commonly existing in the existing perovskite thin films, which reduces the photoelectric conversion efficiency of solar cells, the present application provides a perovskite layer, a preparation method thereof, and a perovskite solar cell.

[0005] In a first aspect, the present application provides a perovskite layer, including an imidazo[2,1-b]thiazole derivative additive shown in Structural Formula 1,

[0006]

[0007] wherein, R 1 is selected from , , , or an alkyl group;

[0008] R 2 , R 3 , and R 4 are each independently selected from one or more of H, an alkoxy group, and an alkyl group which may or may not be substituted by a halogen.

[0009] Preferably, R 1 is selected from an alkyl group having 1 to 3 carbon atoms, , , ; R2 , R 3 , R 4 Each independently selected from one or more of H, an alkoxy group having 1 to 3 carbon atoms, and an alkyl group having 1 to 3 carbon atoms which may or may not be substituted with a fluorine atom.

[0010] Preferably, the imidazo[2,1-b]thiazole derivative additive includes one or more of 6-(4-methoxyphenoxy)-5-nitroimidazo[2,1-b]thiazole, 6-[3-(trifluoromethyl)phenoxy]-5-nitroimidazo[2,1-b]thiazole, 6-(thiophen-2-ylmethoxy)-5-nitroimidazo[2,1-b]thiazole, and 5-nitro-6-(tetrahydrofuran-2-ylmethoxy)imidazo[2,1-b]thiazole.

[0011] Preferably, the molecular formula of the perovskite layer is MA x FA 1-x PbI 3 , 0 < x ≤ 1;

[0012] MA + is CH 3 NH 3 + , FA + is CH(NH 2 ) 2 + .

[0013] In a second aspect, the present application provides a method for preparing the perovskite layer described above, comprising the following steps:

[0014] Under a protective atmosphere, a first solvent, lead iodide, and an imidazo[2,1-b]thiazole derivative additive are mixed uniformly to obtain a lead iodide precursor solution;

[0015] Iodomethylammonium iodide, iodomethylamine, chloromethylamine, and a second solvent are mixed uniformly to obtain an amine salt precursor solution;

[0016] Under a protective atmosphere, the lead iodide precursor solution is annealed for the first time on the electron transport layer to form a lead iodide layer;

[0017] Under a protective atmosphere, the amine salt precursor solution is annealed for the second time on the lead iodide layer to prepare the perovskite layer.

[0018] Preferably, in a protective atmosphere, mixing the first solvent, lead iodide, and an imidazo[2,1-b]thiazole derivative additive uniformly to obtain a lead iodide precursor solution includes the following steps: In a protective atmosphere, adding the lead iodide and the imidazo[2,1-b]thiazole derivative additive to the first solvent, heating and stirring at a temperature of 65-70 °C, and mixing uniformly to obtain the lead iodide precursor solution.

[0019] Preferably, the first solvent includes N,N-dimethylformamide and dimethyl sulfoxide, and the volume ratio of the N,N-dimethylformamide to the dimethyl sulfoxide is (5-9):1;

[0020] The mass concentration of the imidazo[2,1-b]thiazole derivative additive in the lead iodide precursor solution is 0.6-2.5 mg / mL;

[0021] In the lead iodide precursor solution, the molar concentration of the lead iodide is 1.5-1.55 mol / L.

[0022] Preferably, the second solvent includes an alcohol solvent, and the molar ratio of the iodomethylformamidinium, iodomethylammonium, and chloromethylammonium is (53-57):(27-33):(10-20);

[0023] The concentration of the amine salt precursor solution is 0.65-0.7 mol / L.

[0024] Preferably, the spin coating speed of the lead iodide precursor solution on the electron transport layer is 1450-1550 r / min, and the spin coating dosage is 60-120 μL;

[0025] The annealing temperature of the first annealing is 65-70 °C, and the first annealing holding time is 50-65 s;

[0026] The spin coating speed of the amine salt precursor solution on the lead iodide layer is 1800-2000 r / min, and the spin coating dosage is 60-120 μL;

[0027] The annealing temperature of the second annealing is 145-155 °C, and the second annealing holding time is 15-16 min.

[0028] In a third aspect, the present application provides a perovskite solar cell, including the perovskite layer described above or the perovskite layer prepared by the preparation method of the perovskite layer described above.

[0029] The perovskite layer provided by the present application includes an imidazo[2,1-b]thiazole derivative additive shown in Structural Formula 1, contains multiple Lewis base groups, and can react with Pb in the perovskite precursor 2+Lewis acid-base coordination occurs in the solution state, which hinders the coordination crystallization of I - and Pb 2+ , reduces the crystallization rate of perovskite, improves the crystallinity of the perovskite layer, reduces ionic defects, and thus inhibits the non-radiative recombination process, improving the photoelectric conversion efficiency; at the same time, it improves the compactness of the perovskite layer, effectively blocks the intrusion of external water, oxygen, etc., protects the internal structure of the battery from damage, extends the service life, and improves the stability of the battery. Description of the Drawings

[0030] Figure 1 Schematic diagram of each layer structure of the perovskite solar cell provided by this application. Detailed Embodiments

[0031] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further describes the present invention in detail with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] In order to illustrate the technical solutions of the present invention, the following will be described through specific embodiments.

[0033] First, this application provides a perovskite layer, which includes an imidazo[2,1-b]thiazole derivative additive shown in Structural Formula 1,

[0034]

[0035] wherein, R 1 is selected from , , , or an alkyl group;

[0036] R 2 , R 3 , R 4 are each independently selected from one or more of H, an alkoxy group, an alkyl group substituted or unsubstituted by a halogen.

[0037] Specifically, the wavy line represents the meaning of interruption. For example, when R 1 is selected from , or , the carbon at the position of the wavy line containing the meaning of interruption is connected to the carbon in the imidazole. The alkyl group includes a straight-chain alkyl group or a branched alkyl group. The halogen includes the F element.

[0038] Specifically, the imidazo[2,1-b]thiazole derivative additive shown in Structural Formula 1 contains a variety of Lewis base groups, such as imidazole, methoxy, thiazole, nitro, thiophene, furan, etc., which are relative to Pb 2+Functional groups with Lewis basicity, capable of reacting with Pb in the perovskite precursor 2+ to undergo Lewis acid-base coordination in the solution state. During the subsequent crystallization process of the perovskite, this coordination effect hinders the coordination crystallization of I - with Pb 2+ . That is, the imidazo[2,1-b]thiazole derivative additive competes with I - for coordination with Pb 2+ . This competitive relationship increases the coordination crystallization energy barrier of I - with Pb 2+ , which can reduce the crystallization rate of the perovskite, thereby improving the crystallinity of the perovskite layer, reducing ionic defects, further inhibiting the non-radiative recombination process, and enhancing the photoelectric conversion efficiency. At the same time, it enhances the compactness of the perovskite layer, effectively blocks the intrusion of external harmful substances, protects the internal structure of the battery from damage, extends the service life, and improves the stability of the battery.

[0039] The perovskite layer provided by this application includes an imidazo[2,1-b]thiazole derivative additive shown in Structural Formula 1, which contains multiple Lewis base groups and can react with Pb in the perovskite precursor 2+ to undergo Lewis acid-base coordination in the solution state. The effect hinders the coordination crystallization of I - with Pb 2+ , reduces the crystallization rate of the perovskite, improves the crystallinity of the perovskite layer, reduces ionic defects, further inhibits the non-radiative recombination process, and enhances the photoelectric conversion efficiency. At the same time, it improves the compactness of the perovskite layer, effectively blocks the intrusion of external water, oxygen, etc., protects the internal structure of the battery from damage, extends the service life, and improves the stability of the battery.

[0040] In some embodiments, R 1 is selected from one of alkyl groups with 1 to 3 carbon atoms, , , ; each of R 2 , R 3 , R 4 is independently selected from one or more of H, alkoxy groups with 1 to 3 carbon atoms, and alkyl groups with 1 to 3 carbon atoms that are substituted or unsubstituted by fluorine atoms.

[0041] Specifically, the alkoxy groups with 1 to 3 carbon atoms include straight-chain alkoxy groups with 1 to 3 carbon atoms or branched-chain alkoxy groups with 1 to 3 carbon atoms, such as methoxy, ethoxy, and propoxy. The alkyl groups with 1 to 3 carbon atoms include straight-chain alkyl groups with 1 to 3 carbon atoms or branched-chain alkyl groups with 1 to 3 carbon atoms, such as methyl, ethyl, propyl, etc.

[0042] In some embodiments, the imidazo[2,1-b]thiazole derivative additive includes one or more of 6-(4-methoxyphenoxy)-5-nitroimidazo[2,1-b]thiazole (CAS No.: 339008-12-7), 6-[3-(trifluoromethyl)phenoxy]-5-nitroimidazo[2,1-b]thiazole (CAS No.: 339008-08-1), 6-(thiophen-2-ylmethoxy)-5-nitroimidazo[2,1-b]thiazole, and 5-nitro-6-(tetrahydrofuran-2-ylmethoxy)imidazo[2,1-b]thiazole.

[0043] The structural formula of 6-(4-methoxyphenoxy)-5-nitroimidazo[2,1-b]thiazole is ; the structural formula of 6-[3-(trifluoromethyl)phenoxy]-5-nitroimidazo[2,1-b]thiazole is ; the structural formula of 6-(thiophen-2-ylmethoxy)-5-nitroimidazo[2,1-b]thiazole is ; the structural formula of 5-nitro-6-(tetrahydrofuran-2-ylmethoxy)imidazo[2,1-b]thiazole is .

[0044] The several compounds listed above are just a few of them. As long as they conform to the compound shown in Structural Formula 1, they fall within the scope of protection of this application and have the same function.

[0045] The molecular formula of the perovskite layer is MA x FA 1-x PBI 3 , 0 < x ≤ 1; MA + is CH 3 NH 3 + , FA + is CH(NH 2 ) 2 + .

[0046] The molecular formula of the perovskite layer MA x FA 1-x PBI 3 is obtained by spin-coating and annealing the lead iodide precursor solution and the amine salt precursor solution. MA + is the methylammonium ion CH 3 NH 3 + , FA + is the formamidinium ion CH(NH 2 ) 2 + .

[0047] Second aspect, the present application provides a method for preparing a perovskite layer, comprising the following steps:

[0048] Under a protective atmosphere, a first solvent, lead iodide, and an imidazo[2,1-b]thiazole derivative additive are mixed evenly to obtain a lead iodide precursor solution;

[0049] Iodomethylammonium, iodomethylamine, chloromethylamine, and a second solvent are mixed evenly to obtain an amine salt precursor solution;

[0050] Under a protective atmosphere, the lead iodide precursor solution is spin-coated on the electron transport layer, and first annealing is performed to form a lead iodide layer;

[0051] Under a protective atmosphere, the amine salt precursor solution is spin-coated on the lead iodide layer, and second annealing is performed to prepare the perovskite layer.

[0052] For the method for preparing a perovskite layer provided by the present application, an imidazo[2,1-b]thiazole derivative additive and lead iodide are added to a first solvent for dissolution, and are mixed evenly to obtain a lead iodide precursor solution. The lead iodide precursor solution and the amine salt precursor solution are respectively subjected to spin-coating and annealing treatments to obtain the perovskite layer. The preparation process is simple, and a perovskite layer thin film with stronger crystallinity and a flatter surface can be formed on the surface of the electron transport layer. The dangling bond defects on the surface of the perovskite layer between the interface of the electron transport layer and the perovskite layer can be passivated, thereby reducing the binding of deep-level and shallow-level defects to carriers, reducing non-radiative recombination, and improving the photoelectric conversion efficiency; reducing the grain boundary density, improving the compactness of the perovskite layer, being beneficial to blocking the intrusion of water and oxygen, and improving the stability of the perovskite solar cell.

[0053] In some embodiments, under a protective atmosphere, mixing a first solvent, lead iodide, and an imidazo[2,1-b]thiazole derivative additive evenly to obtain a lead iodide precursor solution includes the following steps: under a protective atmosphere, adding the lead iodide and the imidazo[2,1-b]thiazole derivative additive to the first solvent, and performing heating and stirring at a temperature of 65-70 °C to mix evenly to obtain the lead iodide precursor solution.

[0054] Specifically, under a protective atmosphere, when dissolving lead iodide and an imidazo[2,1-b]thiazole derivative additive in a first solvent, a heating and stirring method is adopted, and the heating temperature is controlled within the range of 65-70 °C to accelerate the dissolution rate. Specifically, for example, the heating temperature can be 65 °C, 66 °C, 67 °C, 68 °C, 69 °C, 70 °C, etc., as long as the heating temperature is within the range of 65-70 °C.

[0055] In some embodiments, after obtaining the lead iodide precursor solution by mixing evenly and before spin coating, the lead iodide precursor solution is kept warm at a temperature of 70 - 75°C for 0.5 - 2.5 h.

[0056] Specifically, before spin coating the lead iodide precursor solution, the lead iodide precursor solution is kept warm at 70 - 75°C for 0.5 - 2.5 h to ensure that both lead iodide and the imidazo[2,1 - b]thiazole derivative additive are evenly dissolved in the organic solvent, improving the spin coating efficiency of the lead iodide precursor solution and the flatness of the lead iodide film. Specifically, for example, the holding temperature can be 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, etc., as long as the holding temperature is within the range of 70 - 75°C.

[0057] In some embodiments, the first solvent includes N,N - dimethylformamide and dimethyl sulfoxide, and the volume ratio of N,N - dimethylformamide to dimethyl sulfoxide is (5 - 9):1.

[0058] Specifically, when the volume ratio of N,N - dimethylformamide to dimethyl sulfoxide is within the range of (5 - 9):1, it is beneficial to dissolve lead iodide and the imidazo[2,1 - b]thiazole derivative additive. Specifically, the volume ratio of N,N - dimethylformamide to dimethyl sulfoxide can be 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, or 9:1, etc., as long as the volume ratio of N,N - dimethylformamide to dimethyl sulfoxide is within the range of (5 - 9):1.

[0059] Furthermore, the volume ratio of N,N - dimethylformamide to dimethyl sulfoxide is (6 - 8):1.

[0060] In some embodiments, the mass concentration of the imidazo[2,1 - b]thiazole derivative additive in the lead iodide precursor solution is 0.6 - 2.5 mg / mL.

[0061] Specifically, in the lead iodide precursor solution, the mass concentration of the imidazo[2,1 - b]thiazole derivative additive being 0.6 - 2.5 mg / mL is beneficial for Lewis acid - base coordination with Pb in the perovskite precursor 2+ in the solution state, which hinders the coordination crystallization of I - with Pb 2+ . Specifically, the mass concentration in the lead iodide precursor solution can be 0.6 mg / mL, 0.8 mg / mL, 1.0 mg / mL, 1.2 mg / mL, 1.5 mg / mL, 2.0 mg / mL, 2.3 mg / mL, or 2.5 mg / mL, etc., as long as the mass concentration in the lead iodide precursor solution is within the range of 0.6 - 2.5 mg / mL.

[0062] Furthermore, the mass concentration of the imidazo[2,1-b]thiazole derivative additive in the lead iodide precursor solution is 0.6 - 1.2 mg / mL.

[0063] In some embodiments, the mass concentration of the imidazo[2,1-b]thiazole derivative additive in the lead iodide precursor solution is 1.0 - 2.5 mg / mL.

[0064] Specifically, the preferred mass concentration of the imidazo[2,1-b]thiazole derivative additive is 1.0 - 2.5 mg / mL, which is beneficial for the imidazo[2,1-b]thiazole derivative additive to form Lewis acid-base coordination with Pb 2+ and effectively hinders the coordination crystallization of I - and Pb 2+ .

[0065] In some embodiments, in the lead iodide precursor solution, the molar concentration of lead iodide is 1.5 - 1.55 mol / L.

[0066] Specifically, when the molar concentration of lead iodide is in the range of 1.5 - 1.55 mol / L, lead iodide not only serves as a component of the perovskite layer, which can minimize the defect density, but also can be retained as a passivator at the grain boundaries to a certain extent, helping to reduce the interfacial recombination and improve the stability and photoelectric conversion efficiency of the perovskite. Specifically, the molar concentration of lead iodide can be 1.5 mol / L, 1.51 mol / L, 1.52 mol / L, 1.53 mol / L, 1.54 mol / L or 1.55 mol / L, etc., as long as the molar concentration of lead iodide is within the range of 1.5 - 1.55 mol / L.

[0067] In some embodiments, the second solvent includes alcohol solvents.

[0068] In some preferred embodiments, the second solvent includes isopropyl alcohol.

[0069] In some embodiments, the molar ratio of formamidinium iodide, methylammonium iodide and chloromethylammonium is (53 - 57):(27 - 33):(10 - 20).

[0070] Specifically, by adjusting the molar ratio of formamidinium iodide, methylammonium iodide and chloromethylammonium to (53 - 57):(27 - 33):(10 - 20), the cation composition in the perovskite material can be precisely controlled. For example, formamidinium iodide and methylammonium iodide can form different perovskite phases, such as formamidinium triiodoplumbate (FAPbI 3 ) and methylammonium triiodoplumbate (MAPbI 3), while methylammonium chloride is usually used as an additive to improve the crystallinity and stability of the thin film. By changing the ratios of these ammonium salts, the bandgap, crystallinity, and environmental stability of the perovskite thin film can be optimized, thereby improving the photoelectric conversion efficiency and long-term operating stability of the solar cell.

[0071] In some preferred embodiments, the molar ratio of formamidinium iodide, methylammonium iodide, and methylammonium chloride is (53 - 57):(27 - 33):(12 - 16).

[0072] In a more preferred embodiment, the molar ratio of formamidinium iodide, methylammonium iodide, and methylammonium chloride is 55.7:30:14.3.

[0073] In some embodiments, the concentration of the ammonium salt precursor solution is 0.65 - 0.7 mol / L.

[0074] The concentration range of 0.65 - 0.7 mol / L of the ammonium salt precursor solution helps to control the crystallization process of the perovskite thin film, enabling the grains to grow orderly, reducing the defect density in the thin film, increasing the carrier mobility, reducing non-radiative recombination, and improving the photoelectric conversion efficiency of the perovskite layer. Specifically, the concentration of the ammonium salt precursor solution can be 0.65 mol / L, 0.67 mol / L, 0.68 mol / L, 0.69 mol / L, or 0.7 mol / L, etc., as long as the concentration of the ammonium salt precursor solution is within the range of 0.65 - 0.7 mol / L.

[0075] In some preferred embodiments, the concentration of the ammonium salt precursor solution is 0.7 mol / L.

[0076] In some embodiments, the protective atmosphere includes one or more of nitrogen and noble gases.

[0077] In some embodiments, the spin coating speed of the lead iodide precursor solution on the electron transport layer is 1450 - 1550 r / min, and the spin coating dosage is 60 - 120 μL; controlling the spin coating speed and spin coating dosage of the lead iodide precursor solution on the electron transport layer is beneficial for the uniform spreading of the lead iodide solution on the surface of the electron transport layer, forming a smooth, dense, and moderately thick lead iodide thin film layer.

[0078] In some embodiments, the annealing temperature of the first annealing is 65 - 70 °C, and the first annealing holding time is 50 - 65 s; controlling the annealing temperature and annealing holding time of the first annealing can promote the removal of the solvent in the residual lead iodide solution, eliminate impurities, adjust the crystallinity and crystal morphology, stabilize the crystal structure, increase the electron mobility, and thus improve the overall performance and service life of the perovskite solar cell.

[0079] The lead iodide precursor solution is spin-coated on the electron transport layer under a protective atmosphere and subjected to the first annealing treatment to obtain a lead iodide layer. Then, the lead iodide layer is dried with nitrogen gas, and then the amine salt precursor solution is spin-coated on the lead iodide layer.

[0080] In some embodiments, the spin-coating speed of the amine salt precursor solution on the lead iodide layer is 1800 - 2000 r / min, and the spin-coating dosage is 60 - 120 μL. Controlling the spin-coating speed and spin-coating dosage of the amine salt precursor solution on the lead iodide layer is beneficial for the uniform spreading of the amine salt precursor solution on the surface of the lead iodide layer, forming a smooth, dense, and moderately thick perovskite layer. Specifically, the spin-coating speed of the amine salt precursor solution on the lead iodide layer can be in the range of 1800 - 1850 r / min, 1850 - 1900 r / min, 1900 - 1950 r / min, or 1950 - 2000 r / min.

[0081] In some embodiments, the annealing temperature of the second annealing is 145 - 155 °C, and the holding time of the second annealing is 15 - 16 min. Controlling the annealing temperature and holding time of the second annealing can optimize the microstructure of the perovskite thin film, reduce defects, improve the carrier mobility, and reduce non-radiative recombination, thereby enhancing the photoelectric conversion efficiency and long-term stability of the perovskite solar cell.

[0082] In a third aspect, the present application provides a perovskite solar cell, including the perovskite layer described above or the perovskite layer prepared by the preparation method of the perovskite layer described above.

[0083] In the perovskite solar cell provided by the present application, the imidazo[2,1-b]thiazole derivative additive shown in Structural Formula 1 added to the perovskite layer acts as a nucleating agent during perovskite crystallization, which is used to improve the film-forming property of the perovskite layer, increase the perovskite crystal grains, and reduce the loss of carriers. Its Lewis basic functional group can form coordination bonds with various defects in the perovskite to optimize the lattice structure distorted due to defects and optimize the electron cloud state near the defects, thereby improving the photoelectric performance of the perovskite solar cell.

[0084] In the perovskite solar cell provided by the present application, after connecting the positive and negative electrodes, when the perovskite layer receives continuous light illumination and exciton absorption occurs, the photo-generated carriers flow into the external circuit under the action of the internal potential difference formed by the perovskite layer structure, and a stable photo-generated current can be formed.

[0085] In some embodiments, the perovskite solar cell sequentially includes a conductive base layer, an electron transport layer, a perovskite layer, a hole transport layer, and a metal electrode layer.

[0086] Fourthly, the present application provides a method for preparing a perovskite solar cell, comprising the following steps:

[0087] Perform pretreatment on the conductive base layer;

[0088] Obtain an electron transport layer precursor solution, and spin-coat it on the surface of the conductive base layer to form an electron transport layer;

[0089] Obtain a lead iodide precursor solution, spin-coat the lead iodide precursor solution on the electron transport layer, and perform a first annealing to form a lead iodide layer;

[0090] Obtain an amine salt precursor solution, spin-coat the amine salt precursor solution on the lead iodide layer, and perform a second annealing to prepare the perovskite layer;

[0091] Obtain a hole transport layer precursor solution, and spin-coat it on the perovskite layer to form a hole transport layer;

[0092] Prepare a metal electrode layer on the hole transport layer.

[0093] In some embodiments, performing pretreatment on the conductive base layer includes the following steps: performing etching and zoning treatment on the conductive base layer, and then performing cleaning and drying.

[0094] Performing etching and zoning treatment on the conductive base layer includes the following steps: using a laser engraver to perform etching and zoning treatment on the conductive base layer; cleaning includes the following steps: after the etching and zoning treatment is completed, ultrasonically clean with glass cleaner, deionized water, ethanol, and isopropanol in sequence; drying includes the following steps, after cleaning is completed, blow dry with nitrogen and perform ultraviolet-ozone treatment.

[0095] Obtaining an electron transport layer precursor solution and spin-coating it on the surface of the conductive base layer to form an electron transport layer includes the following steps: diluting a 15% SnO 2 colloidal aqueous solution with deionized water, and the volume ratio of deionized water to SnO 2 colloid is 3.5 - 6.5:1. Then spin-coat the diluted SnO 2 colloidal aqueous solution on the surface of the conductive base layer, perform annealing treatment to obtain an electron transport layer, and then perform drying treatment.

[0096] In some embodiments, obtaining a hole transport layer precursor solution and spin-coating it on the perovskite layer to form a hole transport layer includes the following steps: under a protective atmosphere, spin-coat the hole transport layer precursor solution on the perovskite layer to form a hole transport layer, and after spin-coating, use nitrogen to purge and dry, and then oxidize in an air environment with a humidity of 0% - 9.5% for 10 - 28 h.

[0097] In some embodiments, the preparation method of the hole transport layer precursor solution includes the following steps: dissolving Li-TFSI (lithium bis(trifluoromethanesulfonyl)imide) in acetonitrile as a solvent to prepare a Li-TFSI acetonitrile solution; dissolving Spiro-MeOTAD in chlorobenzene as a solvent, and adding tBP (tetra-tert-butylpyridine) and the above-mentioned Li-TFSI acetonitrile solution, and mixing evenly to obtain a hole transport layer precursor solution.

[0098] In some embodiments, preparing a metal electrode layer on the hole transport layer comprises the following steps: preparing a metal electrode on the hole transport layer using a vacuum evaporation method, thereby completing the preparation of the metal electrode.

[0099] Before preparing the metal electrode, the hole transport layer is firstly subjected to a scraping process, and then the metal electrode is prepared on the hole transport layer by using a vacuum evaporation method.

[0100] The present invention is further described below by way of examples.

[0101] Example 1

[0102] S1: Cut the FTO conductive glass into substrates with a size of 20mm*20mm as the conductive base layer, use a laser engraving machine to etch and partition the conductive base layer, and then use glass cleaner, deionized water, ethanol, and isopropanol ultrasonic cleaning in sequence. After the above cleaning is completed, blow dry with nitrogen and perform UV-ozone treatment for 15 minutes.

[0103] S2: Dilute SnO with a mass fraction of 15% with deionized water 2 Colloidal aqueous solution, deionized water and SnO 2 The volume ratio of the colloid is 5:1. Then the diluted SnO 2 The colloid aqueous solution is spin-coated on the FTO surface of the conductive substrate FTO conductive glass; finally, the spin-coated sample is placed on a hot stage for annealing to obtain SnO 2 The film acts as an electron transport layer and is then subjected to UV-ozone drying.

[0104] S3:

[0105] Prepare the lead iodide precursor solution: The first solvent is a mixed solution of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) with a volume ratio of 7:1. Under a nitrogen atmosphere, lead iodide and the imidazo[2,1-b]thiazole derivative additive 6-(4-methoxyphenoxy)-5-nitroimidazo[2,1-b]thiazole are added to the first solvent, and heated and stirred at 70 °C to obtain a homogeneous lead iodide precursor solution; filter it using a syringe and filter tip combination. The concentration of 6-(4-methoxyphenoxy)-5-nitroimidazo[2,1-b]thiazole is 1.0 mg / mL, and the molar concentration of lead iodide is 1.5 mol / L.

[0106] Prepare the ammonium salt precursor solution: Mix formamidinium iodide, methylammonium iodide, chloromethylammonium and the second solvent isopropyl alcohol (IPA) evenly to obtain an ammonium salt precursor solution with a concentration of 0.7 mol / L, and filter it using a syringe and filter tip combination. Among them, the molar ratio of formamidinium iodide, methylammonium iodide, and chloromethylammonium is 55.7:30:14.3.

[0107] Prepare the perovskite layer: Keep the lead iodide precursor solution at 70 °C for 0.5 h before spin-coating. Under a nitrogen atmosphere, spin-coat the obtained lead iodide precursor solution on the electron transport layer and perform the first annealing treatment to prepare a lead iodide layer; among them, the spin-coating speed is 1500 r / min, the spin-coating dosage is 70 μL, the first annealing temperature is 70 °C, and the first annealing time is 1 minute.

[0108] Under a nitrogen atmosphere, after blowing the surface of the lead iodide layer with nitrogen, spin-coat the obtained ammonium salt precursor solution on the lead iodide layer and perform the second annealing treatment to prepare a perovskite layer; among them, the second annealing temperature is 150 °C, and the second annealing time is 15 minutes.

[0109] S4: Dissolve Li-TFSI (lithium bis(trifluoromethanesulfonyl)imide) in acetonitrile to a concentration of 520 mg / ml to prepare a Li-TFSI acetonitrile solution. Dissolve 0.0723 g of Spiro-MeOTAD in 1 mL of chlorobenzene, add 28.5 μL of tBP (tetra-tert-butylpyridine) and 17.5 μL of the above Li-TFSI acetonitrile solution, stir until completely dissolved, and then filter it using a syringe and filter tip combination to prepare a hole transport layer precursor solution.

[0110] Spin-coat the hole transport layer solution on the perovskite layer. After obtaining the hole transport layer, blow the surface of the sample clean with a nitrogen gas gun, and then oxidize it in an air environment with a humidity of 0%-9.5% for 12 hours.

[0111] And oxidize it in a drying oven for 12 hours to prepare a hole transport layer.

[0112] S5: On the surface of the hole transport layer prepared in step S4, use a laser engraver to etch out an FTO substrate area with a width of 3 mm. Use vacuum evaporation technology to evaporate and prepare a gold (Au) electrode on the etched sample above, and the thickness of the metal electrode layer is 100 nm, thus completing the preparation of the metal electrode layer.

[0113] Example 2

[0114] Most steps of this example are the same as those of Example 1. The difference is that in step S3, when preparing the lead iodide precursor solution, the imidazo[2,1-b]thiazole derivative additive added is different. The type of imidazo[2,1-b]thiazole derivative additive added in Example 2 is 6-[3-(trifluoromethyl)phenoxy]-5-nitroimidazo[2,1-b]thiazole, and the rest is the same as that of Example 1.

[0115] Example 3

[0116] Most steps of this example are the same as those of Example 1. The difference is that in step S3, when preparing the lead iodide precursor solution, the imidazo[2,1-b]thiazole derivative additive added is different. The type of imidazo[2,1-b]thiazole derivative additive added in Example 3 is 6-(thiophen-2-ylmethoxy)-5-nitroimidazo[2,1-b]thiazole, and the rest is the same as that of Example 1.

[0117] Example 4

[0118] Most steps of this example are the same as those of Example 1. The difference is that in step S3, when preparing the lead iodide precursor solution, the imidazo[2,1-b]thiazole derivative additive added is different. The type of imidazo[2,1-b]thiazole derivative additive added in Example 4 is 5-nitro-6-(tetrahydrofuran-2-ylmethoxy)imidazo[2,1-b]thiazole, and the rest is the same as that of Example 1.

[0119] Example 5

[0120] Most steps of this example are the same as those of Example 1. The difference is that in step S3, in the prepared lead iodide precursor solution, the concentration of 6-(4-methoxyphenoxy)-5-nitroimidazo[2,1-b]thiazole is 2.5 mg / mL, and the rest is the same as that of Example 1.

[0121] Example 6

[0122] Most steps of this example are the same as those of Example 1. The difference is that in step S3, in the prepared lead iodide precursor solution, the concentration of 6-(4-methoxyphenoxy)-5-nitroimidazo[2,1-b]thiazole is 0.6 mg / mL, and the rest is the same as that of Example 1.

[0123] Example 7

[0124] Most of the steps in this example are the same as those in Example 1. The difference is that in step S3, the concentration of 6-(4-methoxyphenoxy)-5-nitroimidazo[2,1-b]thiazole in the prepared lead iodide precursor solution is 3.0 mg / mL, and the rest is the same as in Example 1.

[0125] Example 8

[0126] Most of the steps in this example are the same as those in Example 1. The difference is that in step S3, the concentration of 6-(4-methoxyphenoxy)-5-nitroimidazo[2,1-b]thiazole in the prepared lead iodide precursor solution is 0.2 mg / mL, and the rest is the same as in Example 1.

[0127] Comparative Example 1

[0128] Most of the steps in this comparative example are the same as those in Example 1. The difference is that in step S3, the additive added to the prepared lead iodide precursor solution is 1H-imidazole-2-carbonitrile, and the rest is the same as in Example 1.

[0129] Comparative Example 2

[0130] Most of the steps in this comparative example are the same as those in Example 1. The difference is that in step S3, the additive added to the prepared lead iodide precursor solution is imidazo[2,1-b]thiazole, and the rest is the same as in Example 1.

[0131] Test performance:

[0132] The perovskite solar cells prepared in the above examples and comparative examples (15 perovskite solar cells with an effective area of 0.1 cm 2 were prepared in each example and comparative example) were subjected to the following performance tests.

[0133] Using a solar simulator, the short-circuit current density, open-circuit voltage, fill factor, and photoelectric conversion efficiency of the solar cells in the above examples and comparative examples were tested under a simulated 1 standard sunlight environment. The average values of the test results of 15 perovskite solar cells in each example and comparative example were filled into Table 1, and the specific test results are shown in Table 1.

[0134] Table 1

[0135]

[0136] The final battery structures prepared in the above examples and comparative examples are as Figure 1 shown.

[0137] From the test results in Table 1, it can be seen that when comparing Example 1 with Comparative Examples 1-2, for the lead iodide precursor solution in Comparative Example 1, the additive added is 1H-imidazole-2-carbonitrile, which contains an imidazole group. The open-circuit voltage of the battery is low, the photoelectric conversion efficiency is low, and the fill factor is low. For Comparative Example 2, the additive added is imidazo[2,1-b]thiazole. Compared with Comparative Example 1, the fill factor is improved, but the photoelectric conversion efficiency is still poor. It is speculated that adding the imidazo[2,1-b]thiazole derivative additive shown in Structural Formula 1 provided in the present application to the perovskite layer, which contains various Lewis base groups such as imidazole, methoxy, thiazole, nitro, thiophene, furan, etc. These relative to Pb 2+ functional groups with Lewis basicity can react with Pb in the perovskite precursor 2+ to undergo Lewis acid-base coordination in the solution state. During the subsequent crystallization process of the perovskite, this coordination effect hinders the coordination crystallization of I - and Pb 2+ , thereby improving the crystallinity of the perovskite layer, reducing ion defects, and further inhibiting the non-radiative recombination process, enhancing the photoelectric conversion efficiency; at the same time, improving the compactness of the perovskite layer, effectively blocking the intrusion of external water, oxygen, etc., protecting the internal structure of the battery from damage, extending the service life, and improving the stability of the battery.

[0138] When comparing Example 1, 5-6 with Example 7, 8, in Example 7, the concentration of the imidazo[2,1-b]thiazole derivative additive shown in Structural Formula 1 is higher than 0.6 - 2.5 mg / mL, and in Example 8, the concentration of the imidazo[2,1-b]thiazole derivative additive shown in Structural Formula 1 is lower than the range of 0.6 - 2.5 mg / mL. The photoelectric conversion efficiency of the prepared battery is slightly lower, indicating that in the lead iodide precursor solution, when the concentration of the imidazo[2,1-b]thiazole derivative additive shown in Structural Formula 1 is within the range of 0.6 - 2.5 mg / mL, it helps the imidazo[2,1-b]thiazole derivative additive to undergo Lewis acid-base coordination with Pb 2+ and effectively hinders the coordination crystallization of I - and Pb 2+ , thereby improving the photoelectric conversion efficiency of the battery.

[0139] When comparing Example 1-4, by changing the type of the imidazo[2,1-b]thiazole derivative additive, as long as it meets the structure shown in Structural Formula 1, the same effect can be achieved, and it can all undergo Lewis acid-base coordination with Pb 2+ and effectively hinder the coordination crystallization of I - and Pb 2+ , thereby improving the photoelectric conversion efficiency of the battery.

[0140] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A perovskite layer, characterized in that: The additive comprises an imidazo[2,1-B]thiazole derivative shown in structural formula 1, Wherein R1 is selected from , , , one of alkyl; R2, R3, and R4 are each independently selected from one or more of H, alkoxy, and alkyl substituted or unsubstituted by halogen.

2. The perovskite layer according to claim 1, characterized in that R1 is selected from an alkyl group having 1 to 3 carbon atoms, , , One of; R2, R3, and R4 are each independently selected from one or more of H, an alkoxy group having 1 to 3 carbon atoms, and an alkyl group having 1 to 3 carbon atoms which may be substituted with a fluorine atom or which is unsubstituted.

3. The perovskite layer according to claim 1 or 2, characterized in that The imidazo[2,1-B]thiazole derivative additive includes one or more of 6-(4-methoxyphenoxy)-5-nitroimidazo[2,1-B]thiazole, 6-[3-(trifluoromethyl)phenoxy]-5-nitroimidazo[2,1-B]thiazole, 6-(thiophene-2-methoxy)-5-nitroimidazo[2,1-B]thiazole, and 5-nitro-6-(tetrahydrofuran-2-methoxy)imidazo[2,1-B]thiazole.

4. The perovskite layer according to claim 1, characterized in that The molecular formula of the perovskite layer is MA x FA 1-x PbI3, 0<x≤1; MA + CH3NH3 + , F.A. + CH(NH2)2 + .

5. A method for preparing a perovskite layer according to any one of claims 1 to 4, characterized in that: The following steps are involved: Under a protective atmosphere, the first solvent, lead iodide and an imidazo[2,1-B]thiazole derivative additive are uniformly mixed to obtain a lead iodide precursor solution; Evenly mixing iodoformamidine, iodomethylamine, chloromethylamine and a second solvent to obtain an amine salt precursor solution; Under a protective atmosphere, spin-coating the lead iodide precursor solution on the electron transport layer, and performing a first annealing to form a lead iodide layer; Under a protective atmosphere, the amine salt precursor solution is spin-coated on the lead iodide layer, and a second annealing is performed to prepare the perovskite layer.

6. The method for preparing a perovskite layer according to claim 5, characterized in that: Under a protective atmosphere, the first solvent, lead iodide and an imidazo[2,1-B]thiazole derivative additive are mixed uniformly to obtain a lead iodide precursor solution, which comprises the following steps: under a protective atmosphere, the lead iodide and the imidazo[2,1-B]thiazole derivative additive are added to the first solvent, heated and stirred at a temperature of 65-70° C., and mixed uniformly to obtain the lead iodide precursor solution.

7. The method for preparing a perovskite layer according to claim 5, characterized in that: The first solvent includes N,N-dimethylformamide and dimethyl sulfoxide, and the volume ratio of the N,N-dimethylformamide to the dimethyl sulfoxide is (5-9):1; The mass concentration of the imidazo[2,1-B]thiazole derivative additive in the lead iodide precursor solution is 0.6-2.5 mg / mL; In the lead iodide precursor solution, the molar concentration of the lead iodide is 1.5-1.55 mol / L.

8. The method for preparing a perovskite layer according to claim 5, characterized in that: The second solvent includes an alcohol solvent, and the molar ratio of iodoformamidine, iodomethylamine and chloromethylamine is (53-57): (27-33): (10-20); The concentration of the amine salt precursor solution is 0.65-0.7 mol / L.

9. The method for preparing a perovskite layer according to claim 5, characterized in that: The lead iodide precursor solution is spin-coated on the electron transport layer at a spin coating speed of 1450-1550 r / min, and the spin coating amount is 60-120 μL; The annealing temperature of the first annealing is 65-70° C., and the first annealing holding time is 50-65 seconds; The amine salt precursor solution is spin-coated on the lead iodide layer at a spin-coating speed of 1800-2000 r / min, and the spin-coating amount is 60-120 μL; The annealing temperature of the second annealing is 145-155° C., and the second annealing holding time is 15-16 minutes.

10. A perovskite solar cell, characterized in that: A perovskite layer comprising the perovskite layer according to any one of claims 1 to 4 or a perovskite layer prepared by the preparation method of the perovskite layer according to any one of claims 5 to 9.

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