Perovskite layer, preparation method thereof and perovskite solar cell

Abstract

The invention provides a perovskite layer, a preparation method thereof and a perovskite solar cell, and aims to solve the problem that the photoelectric conversion efficiency of the solar cell is reduced due to the fact that ion defects generally exist in an existing perovskite thin film. The perovskite layer comprises an imidazo [2, 1-B] thiazole derivative additive as shown in a structural formula 1, and # imgabs0 #; wherein R1 is selected from one of # imgabs 1 #, # imgabs 2 #, # imgabs 3 # and an alkyl group; r1, R2, R3 and R4 are independently selected from one or more of H, alkoxy and alkyl substituted or unsubstituted by halogen. The perovskite layer provided by the invention contains various Lewis base groups, and can be subjected to Lewis acid-base coordination with Pb < 2 + > in a perovskite precursor in a solution state, so that coordination crystallization of I <-> and Pb < 2 + > is hindered, the crystallization rate of perovskite is reduced, the crystallinity of the perovskite layer is improved, ion defects are reduced, a non-radiative recombination process is further inhibited, and the performance of the perovskite layer is improved. And the photoelectric conversion efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite solar cells, and in particular to a perovskite layer and 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 for their excellent photoelectric conversion efficiency and low production cost. The core of perovskite solar cells lies in the perovskite semiconductor material, which can generate excitons through the photoelectric effect when exposed to 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 substrate 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 film, in perovskite solar cells is often uncontrolled and is affected by many factors. Due to the ionic characteristics and low defect formation energy of metal halide perovskites, various defects are inevitably generated on the surface and grain boundaries of polycrystalline films, leading to 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] In view of the problem of ion defects commonly existing in existing perovskite films, which reduces the photoelectric conversion efficiency of solar cells, the present application provides a perovskite layer and a preparation method thereof, and a perovskite solar cell.

[0005] In a first aspect, the present application provides a perovskite layer, comprising an imidazo[2,1-B]thiazole derivative additive as 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.

[0006] Preferably, R1 is selected from an alkyl group having 1 to 3 carbon atoms, 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 or unsubstituted with a fluorine atom.

[0007] 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-(thiophene-2-methoxy)-5-nitroimidazo[2,1-B]thiazole, and 5-nitro-6-(tetrahydrofuran-2-methoxy)imidazo[2,1-B]thiazole.

[0008] Preferably, the molecular formula of the perovskite layer is MA x FA 1-x PbI3, 0<x≤1; MA is CH3NH2, FA is CH4N2.

[0009] In a second aspect, the present application provides a method for preparing the above-mentioned perovskite layer, comprising the following steps: 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, performing a first annealing on the lead iodide precursor solution on the electron transport layer to form a lead iodide layer; Under a protective atmosphere, the amine salt precursor solution is subjected to a second annealing on the lead iodide layer to prepare the perovskite layer.

[0010] Preferably, under 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 comprises the following steps: under 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.

[0011] Preferably, the first solvent comprises 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.

[0012] Preferably, the second solvent comprises 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.

[0013] Preferably, 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.

[0014] In a third aspect, the present application provides a perovskite solar cell, comprising the perovskite layer described above or a perovskite layer prepared by the method for preparing the perovskite layer described above.

[0015] The perovskite layer provided in the present application includes an imidazo[2,1-B]thiazole derivative additive shown in structural formula 1, which contains a variety of Lewis base groups and can react with Pb in the perovskite precursor. 2+ Lewis acid-base coordination occurs in solution, which hinders the - With Pb 2+ The coordination crystallization reduces the crystallization rate of perovskite, improves the crystallinity of the perovskite layer, reduces ion defects, and thus inhibits the non-radiative recombination process and improves the photoelectric conversion efficiency; at the same time, it improves the density of the perovskite layer, effectively blocks the intrusion of external water, oxygen, etc., protects the internal structure of the battery from damage, prolongs the service life, and improves the stability of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the structure of each layer of the perovskite solar cell provided in this application. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the 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.

[0018] In order to illustrate the technical solution of the present invention, specific embodiments are provided below for illustration.

[0019] In a first aspect, the present application provides a perovskite layer, comprising an imidazo[2,1-B]thiazole derivative additive as 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.

[0020] Specifically, the wavy line represents an interruption, such as R1 is selected from or When the carbon at the position of the wavy line with interruption meaning is connected to the carbon in the imidazole. The alkyl group includes a straight chain alkyl group or an alkyl group with a branch. The halogen includes the F element.

[0021] 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 relatively 2+ Lewis basic functional groups that can react with Pb in the perovskite precursor 2+ Lewis acid-base coordination occurs in the solution state. In the subsequent crystallization of perovskite, this coordination effect hinders the I - With Pb 2+ The coordination crystallization of imidazo[2,1-B]thiazole derivative additives and I - Competition and Pb 2+ coordination, this competitive relationship increases I - With Pb 2+ The coordination crystallization energy barrier can reduce the crystallization rate of perovskite, thereby improving the crystallinity of the perovskite layer, reducing ion defects, and inhibiting the non-radiative recombination process, thereby improving the photoelectric conversion efficiency; at the same time, it can enhance the density of the perovskite layer, effectively block the invasion of external harmful substances, protect the internal structure of the battery from damage, extend the service life, and improve the stability of the battery.

[0022] The perovskite layer provided in the present application includes an imidazo[2,1-B]thiazole derivative additive shown in structural formula 1, which contains a variety of Lewis base groups and can react with Pb in the perovskite precursor. 2+ Lewis acid-base coordination occurs in solution, which hinders the - With Pb 2+ The coordination crystallization reduces the crystallization rate of perovskite, improves the crystallinity of the perovskite layer, reduces ion defects, and thus inhibits the non-radiative recombination process and improves the photoelectric conversion efficiency; at the same time, it improves the density of the perovskite layer, effectively blocks the intrusion of external water, oxygen, etc., protects the internal structure of the battery from damage, prolongs the service life, and improves the stability of the battery.

[0023] In some embodiments, R1 is selected from an alkyl group having 1 to 3 carbon atoms, 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 or unsubstituted with a fluorine atom.

[0024] Specifically, the alkoxy group having 1 to 3 carbon atoms includes a linear alkoxy group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms and having a branch, such as methoxy, ethoxy, and propoxy. The alkyl group having 1 to 3 carbon atoms includes a linear alkyl group having 1 to 3 carbon atoms or an alkyl group having 1 to 3 carbon atoms and having a branch, such as methyl, ethyl, propyl, etc.

[0025] 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-(thiophene-2-methoxy)-5-nitroimidazo[2,1-B]thiazole, and 5-nitro-6-(tetrahydrofuran-2-methoxy)imidazo[2,1-B]thiazole.

[0026] 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-(thiophene-2-methoxy)-5-nitroimidazo[2,1-B]thiazole is ; The structural formula of 5-nitro-6-(tetrahydrofuran-2-methoxy)imidazo[2,1-B]thiazole is .

[0027] The several compounds listed above are only a few of them. As long as they conform to the compound shown in structural formula 1, they all fall within the scope of protection of this application and have the same effect.

[0028] The molecular formula of the perovskite layer is MA x FA 1-x PBI3, 0<x≤1; MA is CH3NH2, FA is CH4N2.

[0029] The molecular formula of the perovskite layer is MA x FA 1-xPBI3 is obtained by spin coating, annealing, etc. of lead iodide precursor solution and amine salt precursor solution. MA is methylamine CH3NH2, and FA is formamidine CH4N2.

[0030] In a second aspect, the present application provides a method for preparing a perovskite layer, comprising the following steps: 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.

[0031] The present application provides a method for preparing a perovskite layer, wherein an imidazo[2,1-B]thiazole derivative additive and lead iodide are added to a first solvent for dissolution and mixed evenly to obtain a lead iodide precursor solution, and the lead iodide precursor solution and the amine salt precursor solution are spin-coated and annealed to obtain a perovskite layer. The preparation process is simple, and a perovskite layer film with stronger crystallinity and a smoother surface can be formed on the surface of an electron transport layer. The dangling bond defects on the surface of the perovskite layer between the electron transport layer and the perovskite layer interface can be passivated, thereby reducing the binding of deep energy level and shallow energy level defects on carriers, reducing non-radiative recombination, and improving photoelectric conversion efficiency; the reduced grain boundary density improves the compactness of the perovskite layer, which is beneficial to blocking the intrusion of water and oxygen, and improving the stability of perovskite solar cells.

[0032] In some embodiments, under a protective atmosphere, mixing a first solvent, lead iodide and an imidazo[2,1-B]thiazole derivative additive uniformly to obtain a lead iodide precursor solution comprises the following steps: under 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.

[0033] Specifically, under a protective atmosphere, when the lead iodide and the imidazo[2,1-B]thiazole derivative additive are dissolved in the first solvent, a heating and stirring method is adopted, and the heating temperature is controlled in the range of 65-70°C to accelerate the dissolution rate. Specifically, 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 in the range of 65-70°C.

[0034] In some embodiments, after the lead iodide precursor solution is uniformly mixed and before spin coating, the lead iodide precursor solution is kept warm at a temperature of 70-75° C. for a time of 0.5-2.5 h.

[0035] Specifically, before the lead iodide precursor solution is spin-coated, the lead iodide precursor solution is kept at 70-75°C for 0.5-2.5 hours to ensure that the lead iodide and the imidazo[2,1-B]thiazole derivative additives are uniformly dissolved in the organic solvent, thereby improving the spin-coating efficiency of the lead iodide precursor solution and the flatness of the lead iodide layer. Specifically, the insulation temperature can be 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, etc., as long as the insulation temperature is within the range of 70-75°C.

[0036] In some embodiments, 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.

[0037] Specifically, the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is in the range of (5-9):1, which is conducive to dissolving lead iodide and imidazo[2,1-B]thiazole derivative additives. 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, as long as the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is in the range of (5-9):1.

[0038] Furthermore, the volume ratio of N,N-dimethylformamide and dimethyl sulfoxide is (6~8):1.

[0039] 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.

[0040] Specifically, in the lead iodide precursor solution, the mass concentration of the imidazo[2,1-B]thiazole derivative additive is 0.6-2.5 mg / mL, which is beneficial to the Pb in the perovskite precursor. 2+ Lewis acid-base coordination occurs in solution, hindering the I - With Pb 2+ Specifically, the mass concentration of 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, as long as the mass concentration of the lead iodide precursor solution is within the range of 0.6 to 2.5 mg / mL.

[0041] 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.

[0042] 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.

[0043] 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 react with Pb 2+ Lewis acid-base coordination occurs, effectively hindering the I - With Pb 2+ Coordination crystallization.

[0044] In some embodiments, in the lead iodide precursor solution, the molar concentration of the lead iodide is 1.5-1.55 mol / L.

[0045] Specifically, the molar concentration of lead iodide is in the range of 1.5 to 1.55 mol / L. Lead iodide not only minimizes defect density as a component of the perovskite layer, but can also be retained in the grain boundary as a passivator to a certain extent, which helps to reduce interface 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 in the range of 1.5 to 1.55 mol / L.

[0046] In some embodiments, the second solvent comprises an alcohol solvent.

[0047] In some preferred embodiments, the second solvent comprises isopropanol.

[0048] In some embodiments, the molar ratio of iodoformamidine, iodomethylamine and chloromethylamine is (53-57): (27-33): (10-20).

[0049] Specifically, by adjusting the molar ratio of iodoformamidine, iodomethylamine, and chloromethylamine to (53-57): (27-33): (10-20), the cation composition in the perovskite material can be precisely controlled. For example, iodoformamidine and iodomethylamine can form different perovskite phases, such as triiodoformamidine lead acid (FAPbI3) and triiodomethylamine lead acid (MAPbI3), while chloromethylamine is usually used as an additive to improve the crystallinity and stability of the film. By changing the ratio of these amine salts, the band gap, crystallinity, and environmental stability of the perovskite film can be optimized, thereby improving the photoelectric conversion efficiency and long-term operation stability of the solar cell.

[0050] In some preferred embodiments, the molar ratio of iodoformamidine, iodomethylamine and chloromethylamine is (53-57): (27-33): (12-16).

[0051] In a more preferred embodiment, the molar ratio of iodoformamidine, iodomethylamine and chloromethylamine is 55.7:30:14.3.

[0052] In some embodiments, the concentration of the amine salt precursor solution is 0.65-0.7 mol / L.

[0053] The concentration of the amine salt precursor solution is in the range of 0.65 to 0.7 mol / L, which helps to control the crystallization process of the perovskite film, allowing the grains to grow in an orderly manner, reducing the defect density in the film, improving the mobility of carriers, reducing non-radiative recombination, and improving the photoelectric conversion efficiency of the perovskite layer. Specifically, the concentration of the amine 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 amine salt precursor solution is in the range of 0.65 to 0.7 mol / L.

[0054] In some preferred embodiments, the concentration of the amine salt precursor solution is 0.7 mol / L.

[0055] In some embodiments, the protective atmosphere includes one or more of nitrogen and a noble gas.

[0056] In some embodiments, 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; controlling the spin coating speed and spin coating amount of the lead iodide precursor solution spin-coated on the electron transport layer is conducive to uniform spreading of the lead iodide solution on the surface of the electron transport layer to form a smooth and dense lead iodide thin film layer with moderate thickness.

[0057] 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 solvent in the residual lead iodide solution, eliminate impurities, adjust the crystallinity and crystal morphology, stabilize the crystal structure, and improve the electron mobility, thereby improving the overall performance and service life of the perovskite solar cell.

[0058] The lead iodide precursor solution is spin-coated on the electron transport layer under a protective atmosphere, and a first annealing treatment is performed to obtain a lead iodide layer. The lead iodide layer is then blown dry with nitrogen gas, and then an amine salt precursor solution is spin-coated on the lead iodide layer.

[0059] In some embodiments, 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; controlling the spin-coating speed and spin-coating amount of the amine salt precursor solution on the lead iodide layer is conducive to the amine salt precursor solution being evenly spread on the surface of the lead iodide layer to form a smooth and dense perovskite layer with moderate thickness. 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.

[0060] In some embodiments, the annealing temperature of the second annealing is 145-155° C., and the second annealing holding time is 15-16 min. The annealing temperature and annealing holding time of the second annealing are controlled to optimize the microstructure of the perovskite film, reduce defects, increase carrier mobility and reduce non-radiative recombination, thereby improving the photoelectric conversion efficiency and long-term stability of the perovskite solar cell.

[0061] In a third aspect, the present application provides a perovskite solar cell, comprising the perovskite layer described above or a perovskite layer prepared by the method for preparing the perovskite layer described above.

[0062] The perovskite solar cell provided in the present application has an imidazo[2,1-B]thiazole derivative additive shown in structural formula 1 added to the perovskite layer, which acts as a condensation nucleus during the crystallization of the perovskite, so as to improve the film-forming property of the perovskite layer and increase the perovskite crystal grain size and reduce the loss of carriers. The Lewis basic functional groups it possesses can form coordination bonds with various defects in the perovskite, thereby optimizing the lattice structure distorted by the defects, and optimizing the electron cloud state near the defects, thereby improving the photoelectric performance of the perovskite solar cell.

[0063] The perovskite solar cell provided in the present application, after the positive and negative electrodes are connected, the perovskite layer enables the perovskite solar cell to receive continuous light and thus absorb excitons, and the photogenerated carriers flow into the external circuit under the action of the internal potential difference formed by the perovskite layer structure, thereby forming a stable photogenerated current.

[0064] In some embodiments, a perovskite solar cell includes, in sequence, a conductive substrate layer, an electron transport layer, a perovskite layer, a hole transport layer, and a metal electrode layer.

[0065] In a fourth aspect, the present application provides a method for preparing a perovskite solar cell, comprising the following steps: Pre-treating the conductive substrate layer; 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; Obtaining a lead iodide precursor solution, spin-coating the lead iodide precursor solution on the electron transport layer, and performing a first annealing to form a lead iodide layer; Obtaining an amine salt precursor solution, spin-coating the amine salt precursor solution on the lead iodide layer, and performing a second annealing to prepare the perovskite layer; Obtaining a hole transport layer precursor solution, and spin coating the solution on the perovskite layer to form a hole transport layer; A metal electrode layer is prepared on the hole transport layer.

[0066] In some embodiments, pre-processing the conductive base layer includes the following steps: etching and partitioning the conductive base layer, and then cleaning and drying.

[0067] The conductive base layer is subjected to etching and partitioning treatment, comprising the following steps: the conductive base layer is subjected to etching and partitioning treatment by using a laser engraving machine; the cleaning comprises the following steps: after the etching and partitioning treatment is completed, ultrasonic cleaning is performed in sequence using glass cleaner, deionized water, ethanol, and isopropanol; the drying comprises the following steps: after the cleaning is completed, drying is performed using nitrogen and ultraviolet-ozone treatment is performed.

[0068] Obtaining an electron transport layer precursor solution, and spin coating the electron transport layer on the surface of the conductive substrate layer comprises the following steps: diluting a 15% SnO2 colloidal aqueous solution with deionized water, and the volume ratio of deionized water to SnO2 colloidal solution is 3.5 to 6.5: 1. Then spin coating the diluted SnO2 colloidal aqueous solution on the surface of the conductive substrate layer, performing annealing treatment to obtain the electron transport layer, and then performing drying treatment.

[0069] In some embodiments, a hole transport layer precursor solution is obtained, and spin coating the hole transport layer on the perovskite layer to form a hole transport layer comprises the following steps: under a protective atmosphere, spin coating the hole transport layer precursor solution on the perovskite layer to form a hole transport layer, after spin coating is completed, the layer is dried by nitrogen purge, and then oxidized in an air environment with a humidity of 0% to 9.5% for 10 to 28 hours.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] The present invention is further described below by way of examples.

[0074] Example 1 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.

[0075] S2: Dilute the SnO2 colloid aqueous solution with a mass fraction of 15% with deionized water, and the volume ratio of deionized water to SnO2 colloid is 5:1. Then spin-coat the diluted SnO2 colloid aqueous solution on the FTO surface of the conductive substrate FTO conductive glass; finally, place the spin-coated sample on a hot stage for annealing to obtain a SnO2 thin film as an electron transport layer, and then perform UV ozone drying.

[0076] S3: Prepare the lead iodide precursor solution: The first solvent is a mixed solution of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in a volume ratio of 7:1. Under a nitrogen atmosphere, add lead iodide and imidazo[2,1-B]thiazole derivative additive 6-(4-methoxyphenoxy)-5-nitroimidazo[2,1-B]thiazole to the first solvent, heat and stir at 70°C, mix evenly to obtain a lead iodide precursor solution; filter with a syringe and filter tip combination, wherein 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.

[0077] Prepare the amine salt precursor solution: mix iodoformamidine, iodomethylamine, chloromethylamine and the second solvent isopropyl alcohol (IPA) evenly to obtain an amine salt precursor solution with a concentration of 0.7 mol / L, and filter it with a syringe and filter nozzle combination. The molar ratio of iodoformamidine, iodomethylamine and chloromethylamine is 55.7:30:14.3.

[0078] Preparation of perovskite layer: Before spin coating of lead iodide precursor solution, the lead iodide precursor solution is kept at 70°C for 0.5h, and the lead iodide precursor solution obtained above is spin coated on the electron transport layer under nitrogen atmosphere, and the first annealing treatment is performed to prepare a lead iodide layer; wherein the spin coating speed is 1500 r / min, the spin coating amount is 70 μL, the first annealing temperature is 70°C, and the first annealing time is 1 minute.

[0079] In a nitrogen atmosphere, after nitrogen is blown onto the surface of the lead iodide layer, the amine salt precursor solution obtained above is spin-coated on the lead iodide layer, and a second annealing treatment is performed to prepare a perovskite layer; wherein the second annealing temperature is 150° C., and the second annealing time is 15 minutes.

[0080] 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 as solvent, 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 filter with a syringe and filter tip combination to prepare a hole transport layer precursor solution.

[0081] The hole transport layer solution was spin-coated on the perovskite layer. After obtaining the hole transport layer, the sample surface was cleaned with a nitrogen air gun and then oxidized in an air environment with a humidity of 0%-9.5% for 12 hours.

[0082] The film was oxidized in a drying oven for 12 hours to prepare a hole transport layer.

[0083] S5: A 3 mm wide FTO substrate area is etched out on the surface of the hole transport layer prepared in step S4 using a laser engraving machine. A gold (Au) electrode is evaporated on the etched sample using vacuum evaporation technology, and the thickness of the metal electrode layer is 100 nm, thereby completing the preparation of the metal electrode layer.

[0084] Example 2 Most of the steps of this embodiment are the same as those of Embodiment 1, except that in step S3, different imidazo[2,1-B]thiazole derivative additives are added to the lead iodide precursor solution. The type of imidazo[2,1-B]thiazole derivative additive added in Embodiment 2 is 6-[3-(trifluoromethyl)phenoxy]-5-nitroimidazo[2,1-B]thiazole, and the rest is the same as Embodiment 1.

[0085] Example 3 Most of the steps of this embodiment are the same as those of Embodiment 1, except that in step S3, different imidazo[2,1-B]thiazole derivative additives are added to the lead iodide precursor solution. The type of imidazo[2,1-B]thiazole derivative additive added in Embodiment 3 is 6-(thiophene-2-methoxy)-5-nitroimidazo[2,1-B]thiazole, and the rest is the same as that of Embodiment 1.

[0086] Example 4 Most of the steps of this embodiment are the same as those of Embodiment 1, except that in step S3, different imidazo[2,1-B]thiazole derivative additives are added to the lead iodide precursor solution. The type of imidazo[2,1-B]thiazole derivative additive added in Embodiment 4 is 5-nitro-6-(tetrahydrofuran-2-methoxy)imidazo[2,1-B]thiazole, and the rest is the same as that of Embodiment 1.

[0087] Example 5 Most of the steps of this embodiment are the same as those of Example 1, except that in step S3, the concentration of 6-(4-methoxyphenoxy)-5-nitroimidazo[2,1-B]thiazole in the prepared lead iodide precursor solution is 2.5 mg / mL, and the rest is the same as in Example 1.

[0088] Example 6 Most of the steps of this embodiment are the same as those of Example 1, except that in step S3, the concentration of 6-(4-methoxyphenoxy)-5-nitroimidazo[2,1-B]thiazole in the prepared lead iodide precursor solution is 0.6 mg / mL, and the rest is the same as in Example 1.

[0089] Example 7 Most of the steps of this embodiment are the same as those of Example 1, except 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.

[0090] Example 8 Most of the steps of this embodiment are the same as those of Example 1, except 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.

[0091] Comparative Example 1 Most of the steps in this comparative example are the same as those in Example 1, except that in step S3, the lead iodide precursor solution is prepared, and the additive added is 1H-imidazole-2-carbonitrile, and the rest is the same as in Example 1.

[0092] Comparative Example 2 Most of the steps in this comparative example are the same as those in Example 1, except that in step S3, the lead iodide precursor solution is prepared, and the additive added is imidazo[2,1-B]thiazole, and the rest is the same as in Example 1.

[0093] Test performance: The perovskite solar cells prepared in the above-mentioned embodiments and comparative examples (15 perovskite solar cells with an effective area of ​​0.1 cm) were prepared in each embodiment and comparative example. 2 The following performance tests were performed on perovskite solar cells.

[0094] The short-circuit current density, open-circuit voltage, fill factor, and photoelectric conversion efficiency of the solar cells of the above-mentioned embodiments and comparative examples were tested under a simulated standard sunlight environment using a solar simulator. The average values ​​of the test results of 15 perovskite solar cells of the embodiments and comparative examples are entered into Table 1. The specific test results are shown in Table 1.

[0095] Table 1

[0096] The battery structure finally prepared in the above-mentioned embodiments and comparative examples is as follows: Figure 1 shown.

[0097] From the test results in Table 1, it can be seen that, in comparison between Example 1 and Comparative Examples 1-2, the lead iodide precursor solution in Comparative Example 1, the additive added is 1H-imidazole-2-carbonitrile, which contains imidazole groups, and the open circuit voltage of the battery is low, the photoelectric conversion efficiency is low, and the filling factor is low; the additive added in Comparative Example 2 is imidazo[2,1-B]thiazole, and relative to Comparative Example 1, the filling factor is improved, but the photoelectric conversion efficiency is still poor; it is speculated that the imidazo[2,1-B]thiazole derivative additive shown in the structural formula 1 provided in the present application is added to the perovskite layer, which contains a variety of Lewis base groups, such as imidazole, methoxy, thiazole, nitro, thiophene, furan, etc., which are relative to Pb 2+ Lewis basic functional groups that can react with Pb in the perovskite precursor 2+ Lewis acid-base coordination occurs in the solution state. In the subsequent crystallization of perovskite, this coordination effect hinders the I - With Pb 2+ The coordination crystallization can improve the crystallinity of the perovskite layer, reduce ion defects, inhibit the non-radiative recombination process, and improve the photoelectric conversion efficiency; at the same time, the density of the perovskite layer can be improved, 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.

[0098] Comparing Examples 1, 5-6 with Examples 7 and 8, the concentration of the imidazo[2,1-B]thiazole derivative additive represented by structural formula 1 added in Example 7 is higher than 0.6-2.5 mg / mL, and the concentration of the imidazo[2,1-B]thiazole derivative additive represented by structural formula 1 in Example 8 is lower than 0.6-2.5 mg / mL. The photoelectric conversion efficiency of the prepared batteries is slightly low, indicating that in the lead iodide precursor solution, the concentration of the imidazo[2,1-B]thiazole derivative additive represented by structural formula 1 added is in the range of 0.6-2.5 mg / mL, which is conducive to the reaction of the imidazo[2,1-B]thiazole derivative additive with Pb 2+ Lewis acid-base coordination occurs, effectively hindering the I - With Pb 2+ The coordination crystallization improves the photoelectric conversion efficiency of the battery.

[0099] Comparing Examples 1-4, changing the type of imidazo[2,1-B]thiazole derivative additives, as long as they satisfy the structure shown in Structural Formula 1, they all have the same effect and can be used with Pb 2+ Lewis acid-base coordination occurs, effectively hindering I - With Pb 2+ Coordination crystallization can improve the photoelectric conversion efficiency of the battery.

[0100] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the technical solutions described in the above embodiments can still be modified, or some of the technical features can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A perovskite layer, It is characterized in that The additive comprises an imidazo[2,1-B]thiazole derivative shown in structural formula 1, ； Among them, R 1 Selected from , one of alkyl; R 2 , R 3 , R 4 Each is independently selected from one or more of H, alkoxy, and alkyl substituted or unsubstituted by halogen.

2. The perovskite layer according to claim 1, It is characterized in that R 1 is selected from an alkyl group having 1 to 3 carbon atoms, One of; R 2 , 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 be substituted with a fluorine atom.

3. The perovskite layer according to claim 1 or 2, It is 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, It is characterized in that The molecular formula of the perovskite layer is MA x FA 1-x PbI 3 , 0<x≤1; MA to CH 3 NH 2 , FA is CH 4 N 2 .

5. A method for preparing a perovskite layer according to any one of claims 1 to 4, It is 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 the perovskite layer according to claim 5, It is 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, It is 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, It is 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, It is 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, It is 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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