A method for preparing a perovskite layer and a photovoltaic device

Abstract

The present application relates to a method for preparing a perovskite layer and a photovoltaic device, the method comprising: a) forming a first solid layer on a substrate from a first precursor material; the first precursor material comprising at least one divalent inorganic cation B, at least one monovalent cation A and halide anions X; b) treating the first solid layer with a second precursor solution to form the perovskite layer, wherein the second precursor solution comprises at least one monovalent cation A, halide anions X and SCN ‑ The present application enables to control the perovskite film formation process, to optimize the grain size and especially to enhance the growth of the perovskite layer on a textured morphology by adding a thiocyanate compound, in particular a mixture of methylammonium chloride (MACI) and methylammonium thiocyanate (MASCN) in the second step of a two-step process.

Description

Technical Field

[0001] This application relates to a method for preparing a perovskite layer, and a photovoltaic device including the perovskite layer. Background Technology

[0002] Perovskite solar cells (PSCs) have attracted widespread attention from academia and industry due to their high efficiency and low cost, and are considered the strongest competitor to crystalline silicon solar cells, currently the mainstream in the photovoltaic market. Currently, the certified efficiency of perovskite single-junction solar cells has reached 25.7%, approaching the highest certified efficiency of crystalline silicon solar cells. Meanwhile, the certified efficiency of two-terminal tandem cells, which combine perovskite photovoltaic materials with crystalline silicon, has reached 29.8%, approaching 30%, showing great market potential. However, currently, high-efficiency PSCs are only available in small areas (1 cm²). 2 However, large-area PSCs or PSC components suffer from significant efficiency degradation. Furthermore, the stability of PSCs remains a major obstacle to their industrialization.

[0003] To obtain high-efficiency and high-stability perovskite sintering materials (PSCs) over large areas, the preparation of high-quality perovskite thin films is crucial. Currently, perovskite layer preparation primarily employs solution methods, which can be further divided into one-step and two-step methods. The one-step method involves dissolving the components of the perovskite light-absorbing layer material in a solvent according to a designed ratio to form a precursor, which is then coated onto a substrate, the solvent removed, and the material heated for crystallization. The two-step method separates the components of the perovskite layer, first depositing an inorganic metal halide, then depositing an organic material, obtaining the material through a contact reaction. Compared to the one-step method, the two-step method offers advantages such as higher substrate compatibility, the ability to deposit thicker perovskite films, and greater design flexibility. However, the two-step method also has drawbacks: incomplete reaction; more defects; and excessively rapid reaction leading to more nucleation and thus smaller grain size. Summary of the Invention

[0004] This application provides a method for preparing a perovskite layer, the method comprising:

[0005] a) Forming a first solid layer on a substrate using a first precursor material; the first precursor material comprises at least one divalent inorganic cation B, at least one monovalent cation A, and a halide anion X;

[0006] b) Treating the first solid layer with a second precursor solution to form the perovskite layer, wherein the second precursor solution contains at least one monovalent cation A, a halide anion X, and SCN. - ;

[0007] The perovskite material has the general formula ABX3, wherein A is at least one monovalent cation, B is at least one divalent inorganic cation, and X is at least one halide anion.

[0008] This application enables control of the perovskite film formation process and optimization of grain size by adding a compound containing thiocyanate, particularly a mixture of methylammonium chloride (MACl) and methylammonium thiocyanate (MASCN), during the second step of the two-step organic salt deposition process. In particular, it can enhance the growth of perovskite layers on textured surfaces.

[0009] In one embodiment, the thickness of the first solid layer is 1 nm to 10 μm.

[0010] In one embodiment, the first solid layer is formed by physical vapor deposition.

[0011] In one embodiment, the first solid layer is formed by thermal evaporation, wherein the volume ratio of AX to BX2 is 0.01-100:1.

[0012] In one embodiment, the first solid layer is formed by a solution method, wherein the solvent used is selected from DMF, DMSO, NMP and combinations thereof, and the solute includes a monovalent cation A and a divalent inorganic cation B, wherein the molar ratio of the monovalent cation A to the divalent inorganic cation B is 0.01-100:1.

[0013] In one embodiment, after the first solid layer is formed, the first solid layer is further subjected to heat treatment.

[0014] In one embodiment, in the second precursor solution, monovalent cations A and SCN... - The molar ratio is 0.1-100:1, preferably 8-12:1.

[0015] In one embodiment, the second precursor solution comprises thiocyanate, preferably selected from MASCN, FASCN, GuASCN, NaSCN, KSCN, or NH4SCN; the solvent is selected from alcohols, preferably isopropanol.

[0016] In one embodiment, the second precursor solution comprises FABr, FAI, MASCN, and MACl, preferably, the molar ratio of FABr+FAI+MACl to MASCN is 7-12:1.

[0017] In one embodiment, treating the first solid layer with a second precursor solution includes:

[0018] The second precursor solution is applied onto the first solid layer, followed by heat treatment.

[0019] In one embodiment, the thickness of the perovskite layer is 10 nm to 20 μm.

[0020] In one embodiment, the monovalent cation A includes CH(NH2)2. +CH3NH3 + C(NH2)3 + Cs + 、Rb + One or more of the following; the divalent inorganic cation B is selected from Pb. 2+ Sn 2+ 、Sr 2+ One or more of the following, wherein the halide anion is selected from Br - I - CI - One or more of them.

[0021] In one embodiment, the substrate is selected from transparent conductive glass substrate, silicon wafer, or organic flexible substrate, and the texture of the substrate is 0nm-10μm.

[0022] This application also provides a photovoltaic device, the photovoltaic device including a photosensitive region having a perovskite layer, the perovskite layer being prepared by the method described above in this application. Attached Figure Description

[0023] Figure 1 An exemplary embodiment for preparing a perovskite solid layer is shown;

[0024] Figure 2 A single-junction photovoltaic device including a transparent or semi-transparent front electrode and a back electrode is schematically shown.

[0025] Figure 3a and Figure 3b The individual structures for a single-junction photovoltaic device are shown separately. Detailed Implementation

[0026] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present application will become clearer and more apparent.

[0027] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0028] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0029] This application provides a method for preparing a perovskite layer, the method comprising:

[0030] a) Forming a first solid layer on a substrate using a first precursor material; the first precursor material comprises at least one divalent inorganic cation B, at least one monovalent cation A, and a halide anion X;

[0031] b) Treating the first solid layer with a second precursor solution to form the perovskite layer, wherein the second precursor solution contains at least one monovalent cation A, a halide anion X, and SCN. - .

[0032] Figure 1 An exemplary embodiment for preparing a perovskite solid layer is shown:

[0033] (1) Provide a substrate;

[0034] (2) The substrate is treated with a first precursor material;

[0035] (3) Form a first solid layer from the first precursor material on the substrate;

[0036] (4) Treat the first solid layer with a second precursor solution;

[0037] (5) The reaction forms a perovskite solid layer.

[0038] In this application, the perovskite layer has no open porosity, and the perovskite material has the general formula ABX3, wherein A is at least one monovalent cation, B is at least one divalent inorganic cation, and X is at least one halide anion.

[0039] In this application, a perovskite layer is formed on a substrate. The substrate can be a transparent conductive glass substrate, a silicon wafer, or an organic flexible substrate, and the texture of the substrate is 0 nm-10 μm. "Substrate texture" is used to characterize the surface properties of the substrate and refers to the height difference between the peaks and troughs of the substrate surface, which can be measured based on microscopic images observed by scanning electron microscopy.

[0040] As used herein, the term "porous" refers to a material in which pores are arranged. Thus, for example, in a porous material, a pore is a volume of material that is not present within the bulk of the material. Individual pores can have the same size or different sizes. Micropores have a width less than 2 nm (i.e., pore size); mesopores have a width from 2 nm to 50 nm (i.e., pore size); and macropores have a width greater than 50 nm (i.e., pore size). Furthermore, nanopores can be considered to have a width less than 1 nm (i.e., pore size). Pores in a material can include both "closed" pores and open pores. A closed pore is a pore in a material that is a non-connected cavity, i.e., a pore that is isolated within the material and not connected to any other pores, and therefore a pore in which fluids exposed to the material cannot enter. On the other hand, an "open pore" allows such fluids to enter. Therefore, open porosity refers to the fraction of the total volume of a porous material in which fluids can flow effectively. Closed pores are thus excluded. The term "open porosity" is interchangeable with the terms "connected porosity" and "effective porosity," and is generally simplified to "porosity" in the art. As used herein, the term "open-pore porosity" refers to a material that has no effective porosity. Therefore, open-pore porosity materials typically lack both macropores and mesopores. However, open-pore porosity materials can include micropores and nanopores. Such micropores and nanopores are generally too small to negatively impact the requirements of materials requiring low porosity.

[0041] The preparation method of this application includes a first step of forming a first solid layer on a substrate with a first precursor material, wherein the first precursor material contains at least one divalent inorganic cation B, at least one monovalent cation A and a halide anion X.

[0042] The first precursor material used to form the first solid layer comprises at least one divalent inorganic cation B, at least one monovalent cation A, and a halide anion X. In one embodiment, the monovalent cation A is selected from FA. + (formamidin, (HC(NH2)2)2)2 + MA + (methylammonium, CH3NH3) + ), GuA + (C(NH2)3 + Guanidinium ion), Cs + 、Rb + These monovalent cations can be a single monovalent cation or a combination of two or more monovalent cations, and may include, for example, monovalent inorganic cations, monovalent organic cations, and combinations thereof. The divalent inorganic cation B can be selected from Pb. 2+ Sn 2+ 、Sr 2+And combinations thereof. These divalent cations can be a single divalent cation, or a combination of two or more divalent cations. Halide anions can be selected from Br. - I - CI - And combinations thereof. These halide anions can be a single halide anion, or a combination of two or more halide anions. For example, the first precursor material may include a combination of at least one compound AX and at least one compound BX2, wherein compound AX may be selected from CsBr, RbCl, MACl, FABr, etc., and combinations thereof; and compound BX2 may be selected from PbI2, SnCl2, etc., and combinations thereof.

[0043] The method for forming a first solid layer from a first precursor material can include physical vapor deposition, such as one or more of thermal evaporation, sputtering, and ion plating. In the first step, the thickness of the first solid layer can be adjusted according to its composition. In the first step, the thickness of the first solid layer can be from 1 nm to 10 μm, preferably 100-700 nm. For example, the first solid layer can be formed by thermal evaporation, wherein the volume ratio of AX to BX2 used is 0.01-100:1.

[0044] The method for forming a first solid layer from a first precursor material may also include a solution method, such as spin coating, coating, blade coating, inkjet printing, or spray coating. In forming the first solid layer by a solution method, the solvent used may be one or more of dimethylformamide (DMF), dimethyl sulfoxide (DMSO), methylpyrrolidone (NMP), etc.; the solute comprises AX and BX2, with an AX:BX2 molar ratio of 0.01-100:1.

[0045] The steps for forming a solid layer using the solution method are as follows: uniformly spread the solution onto the substrate, and remove the solvent by methods such as heating to obtain the solid layer. Taking the spin-coating solution method as an example, the solution is dropped onto the substrate, and the excess solution is ejected by rotating the substrate. After spin coating (the spin coating speed can be 100-10000 revolutions / minute), the remaining solution adsorbed on the substrate is heated (the heating temperature can be 70-150℃) to form a solid layer.

[0046] In one embodiment, after the first solid layer is formed from the first precursor material, the first solid layer is further subjected to a heat treatment. This heat treatment can promote nucleation within the first solid layer, enhance the subsequent reaction with the second precursor solution, and thereby optimize the quality of the formed perovskite film. In one embodiment, the heating temperature can be 50-300°C, and the heating time can be 10 seconds to 1 hour.

[0047] Next, the second step is performed. The first solid layer is treated with a second precursor solution to form a perovskite solid layer. The second precursor solution used in the second step contains at least one monovalent cation A, a halide anion X, and SCN. - In one embodiment, the monovalent cation A is selected from FA. + (formamidin, (HC(NH2)2)2)2 + MA + (methylammonium, CH3NH3) + ), GuA + (C(NH2)3 + Guanidinium ion), Cs + 、Rb + And combinations thereof. These monovalent cations can be a single monovalent cation, or a combination of two or more monovalent cations, and may include, for example, monovalent inorganic cations, monovalent organic cations, and combinations thereof. Halogen anions can be selected from Br. - I - CI - And their combinations. These halide anions can be a single halide anion, or a combination of two or more halide anions.

[0048] In this application, in the second precursor solution, monovalent cation A and SCN... - The molar ratio can be 1:0.01-10, preferably 8-13:1, for example 10:1, 11:1, 12:1. Particularly preferred is that the second precursor solution contains FABr, FAI, MASCN and MACl, and the molar ratio of FABr+FAI+MACl to MASCN can be 7-12:1. In particular, when the molar ratio of FABr+FAI+MACl to MASCN is 9:1, the optimal ratio is formed, and the preparation of the perovskite layer is best.

[0049] The solvent for the second precursor solution can be an alcohol, such as ethanol, isopropanol, butanol, etc., with isopropanol being preferred.

[0050] It should be noted that during the preparation process, the molar ratio of the total amount of monovalent cation A in the first and second steps to the total amount of divalent inorganic cation B in the preparation process is generally 1:1, so that the perovskite layer ABX3 can be finally formed, but it can be 0.5-1.5:1.

[0051] Treating the first solid layer with the second precursor solution includes coating the second precursor solution onto the first solid layer. In one embodiment, the second precursor solution can be deposited after heating the first solid layer. The coating method can include solution dropwise followed by spin coating, large-area coating, etc. Under normal conditions, the second precursor solution can react with the first solid layer.

[0052] In one embodiment, treating the first solid layer with a second precursor solution includes: applying the second precursor solution onto the first solid layer, followed by heat treatment. The heat treatment can promote the formation of the final perovskite phase. This heat treatment can be performed initially in a dry atmosphere at a temperature of 50-150°C and a humidity of 1-10% for 10-1000 seconds to remove residual solvent from the film. Subsequently, heating in air at a temperature of 80-180°C and a humidity of 20-50% for 1-120 minutes is performed.

[0053] Therefore, the thickness of the perovskite solid layer that can be formed is 10 nm to 20 μm.

[0054] This application also provides a photovoltaic device, the photovoltaic device including a photosensitive region having a perovskite layer, the perovskite layer being prepared by the method described above in this application.

[0055] Figure 2 A single-junction photovoltaic device 100 is schematically shown, comprising a transparent or semi-transparent front electrode 101 and a back electrode 102, wherein a photosensitive region 110 is disposed between the front electrode and the back electrode, and wherein the photosensitive region comprises the aforementioned perovskite layer.

[0056] Perovskite materials are configured to act as light absorbers / photosensitizers in the photosensitive region. Furthermore, the perovskite material in the photosensitive region can also be configured to provide charge transport. In this respect, perovskite materials can act not only as light absorbers (i.e., photosensitizers) but also as n-type, p-type, or intrinsic (i-type) semiconductor materials (charge transporters). Therefore, perovskite materials can act as both photosensitizers and n-type semiconductor materials.

[0057] Figure 3a and Figure 3b A separate structure for a single-junction photovoltaic device 100 is shown, wherein the photosensitive region 110 comprises a perovskite material. The photosensitive region 110 includes an n-type region 111 having at least one n-type layer, a p-type region 112 having at least one p-type layer, and a perovskite material layer 113 disposed between the n-type region 111 and the p-type region 112.

[0058] exist Figure 3a and 3bIn the exemplary device structure shown, the front electrode may include a transparent conductive oxide (TCO), such as indium tin oxide (ITO) or fluorine-doped tin oxide (FTO). The n-type region may include one or more n-type material layers, the p-type region may include one or more p-type material layers, and the back electrode may include a high work function metal, such as gold (Au), silver (Ag), nickel (Ni), palladium (Pd), platinum (Pt), or aluminum (Al). Each p-type and n-type material layer may include various p-type and n-type materials known in the art, which will not be described in detail here.

[0059] Examples 1-4

[0060] A mixed film of PbI2 and CsBr with different proportions (the volume ratios of PbI2 and CsBr are shown in Table 1) and a thickness of 600 nm was prepared on a silicon wafer substrate (the textured surface of the substrate is 2-3 μm) using a thermal evaporation method. The film was then heated at 150 °C for 5 min after the mixed film was formed. Subsequently, a second precursor solution was spin-coated onto the film using a solution method. This solution included 2.4 M FABr (formamidinium bromide), 2.4 M FAI (formamidinium iodide), 0.6 M MACl (methylammonium chloride), and 0.6 MMASCN (methylammonium thiocyanate) in a molar ratio of FABr:FAI:MACl:MASCN = 4:4:1:1, and the solvent was isopropanol. After that, it was cured at room temperature to obtain a perovskite layer.

[0061] Performance testing:

[0062] Fabrication of perovskite / HIT tandem solar cell devices:

[0063] (1) Polishing of N-type silicon wafers with a texture of 3 micrometers;

[0064] (2) The front intrinsic amorphous silicon, n-type amorphous silicon, with a total thickness of 25 nm was prepared by PECVD;

[0065] (3) Backside intrinsic amorphous silicon, p-type amorphous silicon, with a total thickness of 20nm;

[0066] (4) Ag grid electrodes are fabricated on the back side by screen printing;

[0067] (5) A transparent conductive oxide layer ITO with a thickness of 50 nm was prepared by sputtering.

[0068] (6) A transparent conductive oxide layer ITO with a thickness of 130 nm was prepared by sputtering.

[0069] (7) NiO2 with a thickness of 40 nm was prepared on the front side by magnetron sputtering;

[0070] (8) Prepare a perovskite layer on the NiO2 layer as described above;

[0071] (9) LiF and C60 layers were prepared sequentially by thermal evaporation, with thicknesses of 10 nm, respectively;

[0072] (10) SnO2 was prepared by atomic layer deposition with a thickness of 100 nm;

[0073] (11) An ITO layer with a thickness of 100 nm was prepared by sputtering.

[0074] (12) An Ag metal grid layer with a thickness of 100 nm was prepared on the front side using a thermal evaporation method to complete the battery fabrication.

[0075] By placing the prepared battery device in a light source with an intensity of 100 mW / cm 2 The current density-voltage curve of the battery was measured under AM 1.5G standard simulated sunlight to obtain the battery's open-circuit voltage V. oc Short-circuit current density J sc The fill factor FF was used to calculate the photoelectric conversion efficiency of the battery, and the results are shown in Table 1.

[0076] Table 1

[0077]

[0078] Examples 6-10 and Comparative Example 1

[0079] A mixed film of PbI2 and CsBr (CsBr:PbI2 = 1:4, volume ratio) with a thickness of 600 nm was prepared on a silicon wafer substrate (textured surface 2-3 μm) using thermal evaporation. The film was then heated at 150 °C for 5 min after its formation. A second precursor solution, comprising FABr, FAI, MASCN, and MACl, was then spin-coated onto the film using a solution method. The concentrations of FABr and FAI were the same (2.4 M), and the concentration of MASCN was 0.6 M. However, the concentration of MASCN was different. The molar ratios of FABr+FAI+MACl to MASCN are shown in Table 2 (the solution in Comparative Example 1 did not contain MASCN). The solvent was isopropanol. The film was then cured at room temperature to obtain a perovskite layer.

[0080] The battery device was prepared and tested in the same manner as in Example 1, and its performance is shown in Table 2.

[0081] Table 2

[0082]

[0083]

[0084] In this system, the optimal ratio of AX (FAI, FABr, and MACl all belong to AX) to SCN salt (i.e., MASCN) is 9:1, which results in the best preparation of the perovskite layer.

[0085] Example 11

[0086] Repeat the steps of Example 2 to prepare a perovskite layer; the difference is that after the film is formed, no heat treatment is performed, but the second precursor solution is directly spin-coated onto the film.

[0087] The battery device was prepared and tested in the same manner as in Example 1, and its performance is shown in Table 3.

[0088] Table 3

[0089]

[0090] The present application has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present application based on these embodiments, all of which fall within the protection scope of the present application.

Claims

1. A method for preparing a perovskite layer, the method comprising: a) Form a first solid layer on the substrate using the first precursor material; The first precursor material comprises at least one divalent inorganic cation B, at least one monovalent cation A, and a halide anion X; after the first solid layer is formed, the first solid layer is subjected to heat treatment; b) Treating the first solid layer with a second precursor solution to form the perovskite layer, wherein the second precursor solution contains at least one monovalent cation A, a halide anion X, and SCN. - ; The perovskite layer has the general formula ABX3, wherein A is at least one monovalent cation, B is at least one divalent inorganic cation, and X is at least one halide anion; The substrate has a texture of 2μm-10μm, and the perovskite layer has no open pores.

2. The method according to claim 1, wherein, The thickness of the first solid layer is 1 nm to 10 μm.

3. The method according to claim 1, wherein, The first solid layer is formed by physical vapor deposition.

4. The method according to claim 3, wherein, The first solid layer is formed by thermal evaporation, wherein the volume ratio of AX to BX2 is 0.01-100:

1.

5. The method according to claim 1, wherein, The first solid layer is formed by a solution method, wherein the solvent used is selected from DMF, DMSO, NMP and combinations thereof, and the solute includes monovalent cation A and divalent inorganic cation B, with a molar ratio of monovalent cation A to divalent inorganic cation B of 0.01-100:

1.

6. The method according to claim 1, wherein, In the second precursor solution, monovalent cations A and SCN - The molar ratio is 0.1-100:

1.

7. The method according to claim 6, wherein, In the second precursor solution, monovalent cations A and SCN - The molar ratio is 8-12:

1.

8. The method according to claim 1, wherein, The second precursor solution includes thiocyanate; the solvent is selected from alcohols.

9. The method according to claim 8, wherein, The thiocyanate is selected from MASCN, FASCN, GuASCN, NaSCN, KSCN, and NH4SCN; the solvent is selected from isopropanol.

10. The method according to claim 1, wherein, The second precursor solution contains FABr, FAI, MASCN, and MACl.

11. The method of claim 10, wherein the molar ratio of FABR+FAI+MACl to MASCN is 7-12:

1.

12. The method according to claim 1, wherein, Treating the first solid layer with the second precursor solution includes: The second precursor solution is applied onto the first solid layer, followed by heat treatment.

13. The method according to claim 1, wherein, The thickness of the perovskite layer is 10 nm to 20 μm.

14. The method according to claim 1, wherein, The monovalent cation A includes CH(NH2)2 + CH3NH3 + C(NH2)3 + Cs + 、Rb + One or more of the following; the divalent inorganic cation B is selected from Pb. 2+ Sn 2+ 、Sr 2+ One or more of the following, wherein the halide anion is selected from Br - I - CI - One or more of them.

15. The method according to claim 1, wherein, The substrate is selected from transparent conductive glass substrate, silicon wafer, and organic flexible substrate.

16. A photovoltaic device comprising a photosensitive region having a perovskite layer, the perovskite layer being prepared by the method of any one of claims 1-15.

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