Preparation method of perovskite thin film and perovskite battery

Abstract

The invention relates to the technical field of photovoltaic cells, and provides a preparation method of a perovskite thin film and a perovskite cell, and the preparation method of the perovskite thin film comprises the steps: preparing a perovskite precursor solution: dissolving cesium iodide, lead iodide and formamidine iodide in dimethyl sulfoxide (DMSO) to obtain a first solution; dissolving molecules with a bipyridine group and a diphosphate group in an N, N-dimethylformamide (DMF) solution to obtain a second solution; mixing the first solution and the second solution to obtain a perovskite precursor solution; preparing a perovskite thin film: coating the perovskite precursor solution on the top surface of a substrate to perform film forming treatment, and performing annealing treatment to obtain the perovskite thin film; the molecules with the bipyridine group and the diphosphate group comprise 2, 2 '-bipyridine-4, 4'-diphosphon.By means of the method, the problems that internal and surface defects exist in the perovskite thin film, carrier transport is limited by the defects, and the photoelectric conversion efficiency of a perovskite cell is restrained can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic cells, and in particular to a method for preparing a perovskite film and a perovskite cell. Background Art

[0002] As the most valuable renewable energy source, solar energy offers advantages such as ease of access and minimal environmental pollution, making it an excellent energy source that can be used by humans for a long time. With increasing awareness of environmental protection, the development of solar photovoltaic power generation technology has been accelerating in recent years.

[0003] Photovoltaic conversion efficiency is a core metric for evaluating the potential of photovoltaic technology. Higher photovoltaic conversion efficiency means a solar cell of the same area and absorbing the same amount of light can generate more electricity. Currently, the photovoltaic conversion efficiency of traditional crystalline silicon cells is approaching its theoretical limit of 29.4%, leaving little room for future efficiency improvements. However, perovskite-crystalline silicon tandem cells, with a theoretical efficiency limit of 43%, are considered the mainstream technology for breaking through the efficiency limits of crystalline silicon single-junction cells. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems of internal and surface defects in perovskite films, which limit carrier transport and inhibit the photoelectric conversion efficiency of perovskite cells. A method for preparing a perovskite film and a perovskite cell are provided. By introducing molecules containing bipyridine and bisphosphate groups as passivators, the defect problems caused by lattice distortion and uncoordinated ions in perovskites can be solved.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for preparing a perovskite film comprises the following steps:

[0007] S1. Preparing a perovskite precursor solution: dissolving cesium iodide, lead iodide, and formamidine iodide in dimethyl sulfoxide (DMSO) to obtain a first solution; dissolving a molecule having a bipyridine group and a bisphosphate group in N,N-dimethylformamide (DMF) solution to obtain a second solution; and mixing the first solution and the second solution to obtain a perovskite precursor solution;

[0008] S2. Preparing a perovskite thin film: coating the perovskite precursor solution on the top surface of the substrate for film formation, and performing annealing to obtain a perovskite thin film;

[0009] The molecule having a bipyridine group and a bisphosphate group includes 2,2′-bipyridine-4,4′-bisphosphate.

[0010] The present invention adopts a method for preparing a perovskite film, which can solve the problem of defects in perovskite caused by lattice distortion and uncoordinated ions by introducing molecules containing bipyridine and diphosphate groups as passivators. The bipyridine group, with its rigid planar structure and π-π conjugated properties, can react with organic cations (such as formamidinium ions FA) in the perovskite lattice. + ) form a tight intermolecular force, effectively filling the gaps at the grain boundaries and inhibiting the ion migration and formation of defect states at the grain boundaries. At the same time, the phosphate oxygen atoms in the diphosphate group have strong coordination ability and can bind to the uncoordinated Pb on the perovskite surface and grain boundaries. 2+ Ion combination forms a stable passivation layer, eliminating the 0 or deep energy level defects caused by I-vacancies, thereby significantly reducing the density of non-radiative recombination centers.

[0011] Through a two-step annealing process and precisely controlled coating parameters, the directional growth of perovskite crystals is controlled and defects in the perovskite film are reduced. During the first low-temperature annealing stage, the solvent molecules (DMSO / DMF) in the precursor solution gradually escape, inducing the directional nucleation of the perovskite mesophase and forming a dense core skeleton. Simultaneously, the passivation agent molecules preferentially adsorb on the surface of the crystal nucleus, repairing the initial nucleation defects. The second high-temperature annealing step drives the transformation of the mesophase into the photoactive α-phase. The bipyridine-bisphosphate molecules, through dynamic anchoring, guide the orderly growth of the crystal lattice along the orientation, inhibit the formation of random dendrites, increase the film grain size, and reduce the number of grain boundaries.

[0012] As a preferred embodiment of the present invention, in step S1, the concentration ranges of the first solution and the second solution are 0.8-1.2 mol / L and 0.05-0.15 mol / L, respectively.

[0013] As a preferred embodiment of the present invention, in step S1, the molar ratio of the first solution to the second solution in the mixed solution is 10:1 to 5:1.

[0014] As a preferred embodiment of the present invention, in step S2, the film forming process includes spin coating, blade coating or slit coating.

[0015] As a preferred embodiment of the present invention, in step S2, the annealing treatment is carried out at a temperature of 100 to 120°C and a vacuum degree of ≤10 -3 The first annealing is carried out under the conditions of Pa; the temperature is 140~160℃ and the vacuum degree is ≤10 - 3 The second annealing treatment was carried out under the conditions of Pa.

[0016] As a preferred embodiment of the present invention, in step S2, the thickness of the perovskite film is 300-600 nm.

[0017] A perovskite cell comprises a substrate, a hole transport layer, a perovskite film prepared by the above-mentioned method for preparing a perovskite film, an electron transport layer and a metal electrode.

[0018] The present invention adopts a perovskite battery, in which the passivated perovskite film constructs an efficient carrier transmission path, reduces charge recombination, increases the open circuit voltage, thereby improving the battery's photoelectric conversion efficiency, and has good stability.

[0019] As a preferred embodiment of the present invention, the perovskite cell comprises a formal perovskite cell or an inverted perovskite cell.

[0020] As a preferred embodiment of the present invention, when the perovskite cell is an inverse perovskite cell, it further includes a hole blocking layer, wherein the hole blocking layer is arranged between the electron transport layer and the metal electrode, the material of the hole blocking layer is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), and the thickness of the hole blocking layer is 5 to 10 nm.

[0021] As a preferred embodiment of the present invention, the hole transport layer 2 comprises nickel oxide (NiO x ), 3-hexylthiophene (P3HT), cuprous thiocyanate (CuSCN), [2-(9h-carbazole-9-yl)ethyl]phosphonic acid (2PACz), [2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid (MeO-2PACz), [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid (Me-4PACz) and [4-(3,6-dimethoxy-9H-carbazole-9-yl)butyl]phosphonic acid (MeO-4PACz).

[0022] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0023] The method for preparing a perovskite precursor solution of the present invention can solve the problem of defects in perovskite caused by lattice distortion and uncoordinated ions by introducing molecules containing bipyridine and diphosphate groups as passivators. The bipyridine group, with its rigid planar structure and π-π conjugated properties, can react with organic cations (such as formamidinium ions FA) in the perovskite lattice. + ) form a tight intermolecular force, effectively filling the gaps at the grain boundaries and inhibiting the ion migration and formation of defect states at the grain boundaries. At the same time, the phosphate oxygen atoms in the diphosphate group have strong coordination ability and can bind to the uncoordinated Pb on the perovskite surface and grain boundaries. 2+ Ion combination forms a stable passivation layer, eliminating the 0The deep energy level defects caused by I-vacancies are eliminated, thereby significantly reducing the density of non-radiative recombination centers. Through a two-step annealing process and precisely controlled coating parameters, the directional growth of perovskite crystals is controlled and the defects of perovskite films are reduced. In the first low-temperature annealing stage, the solvent molecules (DMSO / DMF) in the precursor solution gradually escape, inducing the directional nucleation of the perovskite mesophase and forming a dense crystal core skeleton; at the same time, the passivator molecules preferentially adsorb on the surface of the crystal core to repair the initial nucleation defects. The second high-temperature annealing step drives the transformation of the mesophase to the photoactive α phase. The bipyridine-bisphosphate molecules, through dynamic anchoring, guide the orderly growth of the lattice along the orientation, inhibit the formation of random dendrites, increase the grain size of the film, and reduce the number of grain boundaries.

[0024] The perovskite cell described in the present invention has a passivated perovskite film that constructs an efficient carrier transmission path, reduces charge recombination, increases the open circuit voltage, thereby improving the photoelectric conversion efficiency of the cell, and has good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a preparation flow chart of a method for preparing a perovskite thin film;

[0026] Figure 2 This is a schematic diagram of the structure of a perovskite battery;

[0027] Icon: 1-substrate; 2-hole transport layer; 3-perovskite film; 4-electron transport layer; 5-metal electrode. DETAILED DESCRIPTION

[0028] The present invention will be described in detail below with reference to the accompanying drawings.

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0030] Example 1

[0031] like Figure 1 As shown, the method for preparing a perovskite film adopted in the present invention comprises the following steps:

[0032] S1. Preparing a perovskite precursor solution: dissolving cesium iodide, lead iodide, and formamidine iodide in dimethyl sulfoxide (DMSO) to obtain a first solution; dissolving a molecule having a bipyridine group and a bisphosphate group in N,N-dimethylformamide (DMF) solution to obtain a second solution; and mixing the first solution and the second solution to obtain a perovskite precursor solution;

[0033] S2, preparing a perovskite thin film: coating the perovskite precursor solution on the top surface of the substrate for film formation, and performing annealing to obtain a perovskite thin film 3;

[0034] The molecule having a bipyridine group and a bisphosphate group includes 2,2′-bipyridine-4,4′-bisphosphate.

[0035] Furthermore, in step S1, the concentration ranges of the first solution and the second solution are 0.8-1.2 mol / L and 0.05-0.15 mol / L, respectively.

[0036] Furthermore, in step S1, the molar ratio of the first solution to the second solution in the mixed solution is 10:1 to 5:1.

[0037] Furthermore, in step S2, the film forming process includes spin coating, blade coating or slit coating.

[0038] Furthermore, in step S2, the annealing treatment is specifically performed by performing a first annealing treatment at a temperature of 100-120° C. and a vacuum degree of ≤10-3Pa; and performing a second annealing treatment at a temperature of 140-160° C. and a vacuum degree of ≤10-3Pa.

[0039] Furthermore, in step S2, the thickness of the perovskite film 3 is 300-600 nm.

[0040] By introducing molecules containing bipyridine and diphosphate groups as passivators, the defect problem caused by lattice distortion and uncoordinated ions in perovskites can be solved. The bipyridine group, with its rigid planar structure and π-π conjugated properties, can react with organic cations (such as formamidinium ions FA) in the perovskite lattice. + ) form a tight intermolecular force, effectively filling the gaps at the grain boundaries and inhibiting the ion migration and formation of defect states at the grain boundaries. At the same time, the phosphate oxygen atoms in the diphosphate group have strong coordination ability and can bind to the uncoordinated Pb on the perovskite surface and grain boundaries. 2+ Ion combination forms a stable passivation layer, eliminating the 0 or I -Vacancies cause deep energy level defects, significantly reducing the density of non-radiative recombination centers. Through a two-step annealing process and precisely controlled coating parameters, the directional growth of perovskite crystals is controlled, reducing defects in perovskite films. During the first low-temperature annealing stage, solvent molecules (DMSO / DMF) in the precursor solution gradually escape, inducing directional nucleation of the perovskite mesophase and forming a dense core skeleton. At the same time, passivator molecules preferentially adsorb on the surface of the crystal nucleus to repair initial nucleation defects. The second high-temperature annealing step drives the mesophase to transform into the photoactive α phase. Bipyridine-bisphosphate molecules, through dynamic anchoring, guide the lattice to grow in an orderly manner along the orientation, inhibit the formation of random dendrites, increase the grain size of the film, and reduce the number of grain boundaries.

[0041] In this embodiment, the perovskite precursor solution is prepared by dissolving 0.8 mmol CsI, 0.2 mmol FAI, and 1 mmol PbI2 in 1 mL DMSO and stirring until completely dissolved to obtain the first solution (concentration 1.0 mol / L); 0.1 mmol 2,2'-bipyridine-4,4'-bisphosphate is dissolved in 1 mL DMF to obtain a second solution (concentration 0.1 mol / L); the first solution and the second solution are mixed in a molar ratio of 8:1, and magnetic stirring is performed for 2 hours to obtain a uniform perovskite precursor solution.

[0042] Preparation of perovskite film: The prepared perovskite precursor solution was added dropwise to the substrate surface and spin-coated at 4000 rpm for 30 seconds to form a film; the sample was placed in a vacuum oven at 110°C and 10 -3 The first stage annealing was carried out under the conditions of Pa for 12 minutes; the second stage annealing was carried out at 150℃ and 10 -3 The film was treated under Pa conditions for 25 minutes, and finally a perovskite film 3 with a thickness of about 450 nm was obtained.

[0043] Example 2

[0044] like Figure 2 As shown, a perovskite cell used in the present invention, based on Example 1, comprises a substrate 1, a hole transport layer 2, a perovskite film 3 prepared by the preparation method of a perovskite film as described in Example 1, an electron transport layer 4 and a metal electrode 5.

[0045] Furthermore, the perovskite cell includes a formal perovskite cell or an inverted perovskite cell.

[0046] Furthermore, when the perovskite cell is an inverse perovskite cell, it also includes a hole blocking layer, which is arranged between the electron transport layer 4 and the metal electrode 5. The material of the hole blocking layer is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), and the thickness of the hole blocking layer is 5 to 10 nm.

[0047] Furthermore, the hole transport layer 2 comprises nickel oxide (NiO x ), 3-hexylthiophene (P3HT), cuprous thiocyanate (CuSCN), [2-(9h-carbazole-9-yl)ethyl]phosphonic acid (2PACz), [2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid (MeO-2PACz), [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid (Me-4PACz) and [4-(3,6-dimethoxy-9H-carbazole-9-yl)butyl]phosphonic acid (MeO-4PACz).

[0048] The passivated perovskite film 3 constructs an efficient carrier transmission path, reduces charge recombination, increases the open circuit voltage, thereby improving the photoelectric conversion efficiency of the battery and has good stability.

[0049] In this embodiment, taking the inverse perovskite cell as an example, a P3HT solution was spin-coated on an ITO substrate 1 (3000 rpm, 30 seconds) to form a hole transport layer 2 with a thickness of 40 nm; a perovskite film 3 was prepared by the preparation method as in Example 1; and then a PCBM solution was spin-coated (2000 rpm, 20 seconds) to form an electron transport layer 4 with a thickness of 50 nm; a silver electrode with a thickness of 90 nm was vacuum evaporated to complete the preparation of the inverse perovskite cell.

[0050] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a perovskite thin film, characterized in that: The following steps are involved: S1. Preparing a perovskite precursor solution: dissolving cesium iodide, lead iodide, and formamidine iodide in dimethyl sulfoxide (DMSO) to obtain a first solution; dissolving a molecule having a bipyridine group and a bisphosphate group in N,N-dimethylformamide (DMF) solution to obtain a second solution; and mixing the first solution and the second solution to obtain a perovskite precursor solution; S2. Preparing a perovskite thin film: coating the perovskite precursor solution on the top surface of the substrate for film formation, and performing annealing to obtain a perovskite thin film; The molecule having a bipyridine group and a bisphosphate group includes 2,2′-bipyridine-4,4′-bisphosphate.

2. The method for preparing a perovskite thin film according to claim 1, wherein: In step S1, the concentration ranges of the first solution and the second solution are 0.8-1.2 mol / L and 0.05-0.15 mol / L, respectively.

3. The method for preparing a perovskite thin film according to claim 1, wherein: In step S1, the molar ratio of the first solution to the second solution in the mixed solution is 10:1 to 5:

1.

4. The method for preparing a perovskite thin film according to claim 1, wherein: In step S2, the film forming process includes spin coating, blade coating or slit coating.

5. The method for preparing a perovskite thin film according to claim 1, wherein: In step S2, the annealing treatment is carried out at a temperature of 100 to 120°C and a vacuum degree of ≤10 -3 The first annealing is carried out under the conditions of Pa; the temperature is 140~160℃ and the vacuum degree is ≤10 -3 The second annealing treatment was carried out under the conditions of Pa.

6. The method for preparing a perovskite thin film according to claim 1, wherein: In step S2, the thickness of the perovskite film is 300-600 nm.

7. A perovskite battery, characterized in that: The perovskite cell comprises a substrate, a hole transport layer, a perovskite film prepared by the method for preparing a perovskite film according to any one of claims 1 to 6, an electron transport layer and a metal electrode.

8. The perovskite battery according to claim 7, characterized in that: The perovskite cell includes a formal perovskite cell or an inverted perovskite cell.

9. The perovskite battery according to claim 8, characterized in that: When the perovskite cell is an inverted perovskite cell, it further includes a hole blocking layer, which is arranged between the electron transport layer and the metal electrode. The material of the hole blocking layer is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), and the thickness of the hole blocking layer is 5 to 10 nm.

10. The perovskite battery according to any one of claims 7 to 9, characterized in that: The hole transport layer 2 comprises nickel oxide (NiO x ), 3-hexylthiophene (P3HT), cuprous thiocyanate (CuSCN), [2-(9h-carbazole-9-yl)ethyl]phosphonic acid (2PACz), [2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid (MeO-2PACz), [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid (Me-4PACz) and [4-(3,6-dimethoxy-9H-carbazole-9-yl)butyl]phosphonic acid (MeO-4PACz).

Images