Method for preparing perovskite absorption layer by gradient co-evaporation and tandem solar cell

Abstract

A method for preparing a perovskite absorption layer by gradient co-evaporation and a tandem solar cell. Said method comprises the following steps: providing a textured substrate; using an evaporation method to prepare on the textured substrate a hybrid film, the hybrid film comprising lead iodide and cesium bromide, the evaporation deposition rate of lead iodide maintaining a constant acceleration during the coating process, the content of lead iodide gradiently increasing from a buried bottom surface to the upper surface of the hybrid film, the evaporation deposition rate of cesium bromide maintaining a constant deceleration during the coating process, and the content of cesium bromide gradiently decreasing from the buried bottom surface to the upper surface of the hybrid film; preparing an ammonium salt precursor solution; and coating the surface of the hybrid film with the ammonium salt precursor solution, so as to prepare a perovskite absorption layer.

Description

Method for preparing perovskite absorption layer by gradient co-evaporation and stacked solar cell

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on September 27, 2023, with application number 202311270645.2 and invention name “A method for preparing a perovskite absorption layer by gradient co-evaporation and a stacked solar cell”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of solar cells, and in particular to a method for preparing a perovskite absorption layer through gradient co-evaporation and a stacked solar cell. Background Art

[0003] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0004] Currently, most existing crystalline silicon / perovskite tandem solar cells are made based on polished crystalline silicon bottom cells. This is because existing high-efficiency perovskite film formation methods are generally targeted at polished substrates. However, the surfaces of crystalline silicon bottom cells that have been commercialized on a large scale are mostly velvet-like. The velvet-like surface can greatly reduce the reflection of incident light by crystalline silicon / perovskite tandem solar cells, improving light absorption, which is one of the indispensable conditions for high-efficiency solar cells. Therefore, the crystalline silicon / perovskite tandem solar cells based on polished velvet-like crystalline silicon bottom cells currently have large light absorption losses and low short-circuit current density.

[0005] However, for textured crystalline silicon bottom cells, due to the unique unevenness of the substrate, the perovskite film prepared using a solution wet method cannot conformally cover the textured crystalline silicon substrate, resulting in a short circuit in the crystalline silicon / perovskite tandem solar cell. In order to prepare a conformal, fully covered perovskite film on a textured crystalline silicon substrate, a two-step evaporation and solution method is usually used. In the first step, a conformal lead iodide-cesium bromide mixed film is prepared by evaporation. In the second step, a mixed ammonium salt solution is reacted with the mixed film to form a conformal perovskite film.

[0006] However, using the traditional two-step preparation method, the lead iodide near the top surface of the conformal hybrid film is more likely to react completely with the ammonium salt solution. The lead iodide near the buried bottom surface of the conformal hybrid film, because it is not in direct contact with the ammonium salt solution, is less likely to react completely, and ultimately forms a large amount of lead iodide residue in the lower layer of the perovskite film. This free lead iodide will form a large number of defects in the perovskite film, resulting in low-quality perovskite films, thereby affecting the performance of crystalline silicon / perovskite tandem solar cells. Application Contents

[0007] The purpose of the embodiments of the present application is to provide a method for preparing a perovskite absorption layer by gradient co-evaporation and a tandem solar cell, including but not limited to solving the problem that free lead iodide forms a large number of defects in the perovskite film, resulting in low quality of the formed perovskite film, thereby affecting the performance of the crystalline silicon / perovskite tandem solar cell.

[0008] The technical solution adopted in the embodiment of this application is:

[0009] In a first aspect, a method for preparing a perovskite absorption layer by gradient co-evaporation is provided, comprising the steps of:

[0010] providing a suede base;

[0011] A mixed film is prepared on the suede substrate by an evaporation method; wherein the mixed film includes lead iodide and cesium bromide, the evaporation rate of the lead iodide maintains a constant increasing rate during the coating process, and the content of the lead iodide increases gradually from the buried bottom surface to the upper surface of the mixed film; the evaporation rate of the cesium bromide maintains a constant decreasing rate during the coating process, and the content of the cesium bromide decreases gradually from the buried bottom surface to the upper surface of the mixed film;

[0012] preparing an ammonium salt precursor solution;

[0013] The ammonium salt precursor solution is coated on the surface of the mixed film to prepare a perovskite absorption layer.

[0014] In one embodiment, during the coating process, the ratio of the evaporation rate of the lead iodide to the evaporation rate of the cesium bromide is a constant value, and the constant value is between 10:1 and 2:1.

[0015] In one embodiment, the evaporation rate of the lead iodide maintains a constant increasing rate between 0-10 A / s, and the constant increasing rate of the lead iodide is between 0.001 A / s and 0.01 A / s; the evaporation rate of the cesium bromide maintains a constant decreasing rate between 0 A / s and 10 A / s, and the constant decreasing rate of the cesium bromide is between -0.01 A / s and 0 A / s.

[0016] In one embodiment, in the step of preparing the ammonium salt precursor solution: the ammonium salt precursor solution is prepared by dissolving ABX3 structured perovskite in an organic solvent.

[0017] In one embodiment, in the ABX3 structured perovskite, the A position is an organic cation, including CH3NH3 + (MA + ), NH2CH=NH2 + (FA + ), CH3CH2NH3 + or Cs +At least one of; B position is a metal cation, including Pb 2+ 、Sn 2+ At least one of; X is a halogen anion, including F - 、Cl - Br - , I - At least one of .

[0018] In one embodiment, the organic solvent includes at least one of ethanol, isopropanol, methanol, dimethylformamide (DMF), g-butyrolactone (GBL), dimethyl sulfoxide (DMSO) and N,N-dimethylacetamide.

[0019] In one embodiment, in the step of coating the ammonium salt precursor solution on the surface of the mixed film to prepare the perovskite absorption layer: the ammonium salt precursor solution is coated on the surface of the mixed film by spin coating; and annealing is performed after the spin coating is completed.

[0020] In a second aspect, a stacked solar cell is provided, comprising:

[0021] A crystalline silicon bottom cell, comprising a base electrode layer, a P-type base doping layer disposed on a top surface of the base electrode layer, a base bottom surface passivation layer disposed on a top surface of the P-type base doping layer, a textured silicon substrate disposed on a top surface of the base bottom surface passivation layer, a base surface passivation layer disposed on a top surface of the textured silicon substrate, an N-type base doping layer disposed on a top surface of the base surface passivation layer, and a tunneling layer disposed on a top surface of the N-type base doping layer;

[0022] A perovskite top cell, comprising a hole transport layer disposed on the top surface of the tunneling layer, a perovskite absorption layer disposed on the top surface of the hole transport layer, a perovskite passivation layer disposed on the top surface of the perovskite absorption layer, an electron transport layer disposed on the top surface of the perovskite passivation layer, a buffer layer disposed on the top surface of the electron transport layer, and a surface electrode layer disposed on the top surface of the buffer layer;

[0023] Wherein, the perovskite absorption layer is prepared by the method for preparing the perovskite absorption layer by gradient co-evaporation as described in any one of claims 1 to 7.

[0024] In one embodiment, the base electrode layer includes a first metal electrode layer and a first transparent electrode layer disposed on the top surface of the first metal electrode layer; the P-type base doping layer is disposed on the top surface of the first transparent electrode layer.

[0025] In one embodiment, the surface electrode layer includes a second transparent electrode layer disposed on the top surface of the buffer layer and a second metal electrode layer disposed on the top surface of the second transparent electrode layer.

[0026] In one embodiment, the first transparent electrode layer and the second transparent electrode layer are at least one of indium tin oxide (ITO), indium zinc oxide (IZO), and aluminum zinc oxide (AZO).

[0027] In one embodiment, the second metal electrode layer is at least one of silver (Ag), gold (Au), copper (Cu), aluminum (Al), and carbon (C).

[0028] In one embodiment, the tandem solar cell further includes an anti-reflection layer disposed on the top surface of the surface electrode layer.

[0029] In one embodiment, the anti-reflection layer is at least one of magnesium fluoride, lithium fluoride (LiF), sodium fluoride (NaF), and silicon oxide (SiO2).

[0030] In one embodiment, the perovskite passivation layer is at least one of propylenediamine iodide, propylenediamine bromide (PDADBr), butylammonium chloride (BACl), butylammonium bromide (BABr), butylammonium iodide (BAI), N,N-dimethyl-1,3-propylenediamine hydrochloride (DMePDADCl), and dodecanediamine bromide (DDDADBr); or, the perovskite passivation layer is at least one of magnesium fluoride, lithium fluoride (LiF), and sodium fluoride (NaF).

[0031] In one embodiment, the electron transport layer is zinc oxide (ZnO), tin dioxide (SnO2), titanium dioxide (TiO2), [6,6]-phenyl C61 butyric acid methyl ester (PC 61 BM), carbon 60 (C 60 ), at least one of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP).

[0032] In one embodiment, the buffer layer is at least one of zinc oxide (ZnO), tin dioxide (SnO2), and titanium dioxide (TiO2).

[0033] In one embodiment, the crystalline silicon bottom cell and the perovskite top cell are arranged in series.

[0034] The beneficial effects of the method for preparing a perovskite absorber layer by gradient co-evaporation and the stacked solar cell provided in the embodiments of the present application are as follows: by gradiently adjusting the evaporation rates of lead iodide and cesium bromide, the content of lead iodide gradually increases from the buried bottom surface to the upper surface of the mixed film, and the content of cesium bromide gradually decreases from the buried bottom surface to the upper surface of the mixed film. This allows the lead iodide to react more completely with the ammonium salt precursor solution, reduces the lead iodide residue on the buried bottom surface of the mixed film, and thus forms a high-quality, low-defect-density perovskite absorber layer, thereby improving the performance of the stacked solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or exemplary technical descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0036] FIG1 is a schematic structural diagram of a stacked solar cell provided in an embodiment of the present application;

[0037] FIG2 is a schematic diagram of an equivalent structural flow chart of a method for preparing a perovskite absorption layer by gradient co-evaporation provided in an embodiment of the present application;

[0038] FIG3 is a graph showing the relationship between the evaporation rates of lead iodide and cesium bromide and time, respectively, provided in an embodiment of the present application;

[0039] FIG4 is a graph showing the relationship between the evaporation rates of lead iodide and cesium bromide and time, respectively, provided in Comparative Example 1;

[0040] FIG5 is a graph showing the relationship between the evaporation rates of lead iodide and cesium bromide and time, respectively, provided in Comparative Example 2;

[0041] FIG6 is a graph showing the relationship between the evaporation rates of lead iodide and cesium bromide and time, respectively, provided in Comparative Example 3.

[0042] Among them, the main marks of the drawings in the figure are:

[0043] 1. Crystalline silicon bottom cell; 11. Base electrode layer; 111. First metal electrode layer; 112. First transparent electrode layer; 12. P-type base doping layer; 13. Base bottom passivation layer; 14. Textured silicon substrate; 15. Base surface passivation layer; 16. N-type base doping layer; 17. Tunneling layer;

[0044] 2. Perovskite top cell; 21. Hole transport layer; 22. Perovskite absorption layer; 23. Perovskite passivation layer; 24. Electron transport layer; 25. Buffer layer; 26. Surface electrode layer; 261. Second transparent electrode layer; 262. Second metal electrode layer; 27. Anti-reflection layer;

[0045] 100, suede base; 200, mixed film. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is 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 this application.

[0047] It should be noted that when a component is referred to as being "fixed on" or "disposed on" another component, it may be directly on the other component or indirectly on the other component. When a component is referred to as being "connected to" another component, it may be directly or indirectly connected to the other component. The terms "upper", "lower", "left", "right", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of description and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this application. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances. The terms "first" and "second" are only used for the purpose of convenience of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0048] In order to illustrate the technical solution provided by this application, a detailed description is given below with reference to specific drawings and embodiments.

[0049] In the traditional two-step process for preparing perovskite films, the lead iodide near the top surface of the conformal hybrid film 200 is more likely to react completely with the ammonium salt solution. However, the lead iodide near the bottom surface of the conformal hybrid film 200, which is not in direct contact with the ammonium salt solution, is less likely to react completely, ultimately forming a large amount of lead iodide residue in the lower layer of the perovskite film. This free lead iodide can form numerous defects within the perovskite film, resulting in low-quality perovskite films and thus affecting the performance of crystalline silicon / perovskite tandem solar cells.

[0050] Based on this, the present application provides a method for preparing a perovskite absorption layer by gradient co-evaporation and a stacked solar cell to solve the above problems.

[0051] Referring to FIG1 , the stacked solar cell provided in an embodiment of the present application will now be described. The stacked solar cell includes a crystalline silicon bottom cell 1 and a perovskite top cell 2 disposed above the crystalline silicon bottom cell 1. The crystalline silicon bottom cell 1 includes a base electrode layer 11, a P-type base doping layer 12 disposed on the top surface of the base electrode layer 11, a base bottom surface passivation layer 13 disposed on the top surface of the P-type base doping layer 12, a textured silicon substrate 14 disposed on the top surface of the base bottom surface passivation layer 13, a base surface passivation layer 15 disposed on the top surface of the textured silicon substrate 14, an N-type base doping layer 16 disposed on the top surface of the base surface passivation layer 15, and a tunneling layer 17 disposed on the top surface of the N-type base doping layer 16.

[0052] The perovskite top cell 2 includes a hole transport layer 21 disposed on the top surface of the tunneling layer 17, a perovskite absorption layer 22 disposed on the top surface of the hole transport layer 21, a perovskite passivation layer 23 disposed on the top surface of the perovskite absorption layer 22, an electron transport layer 24 disposed on the top surface of the perovskite passivation layer 23, a buffer layer 25 disposed on the top surface of the electron transport layer 24, and a surface electrode layer 26 disposed on the top surface of the buffer layer 25. The perovskite absorption layer 22 is prepared by a method for preparing the perovskite absorption layer 22 by gradient co-evaporation. The perovskite passivation layer 23 can separate the perovskite absorption layer 22 from the electron transport layer 24 to prevent mutual influence. The electron transport layer 24 plays an important role in transporting electrons and blocking electron-hole recombination. The buffer layer 25 can separate the electron transport layer 24 from the surface electrode layer 26 to prevent mutual interference between the two.

[0053] In one embodiment, referring to FIG. 1 , as a specific implementation of a tandem solar cell provided in an embodiment of the present application, the base electrode layer 11 includes a first metal electrode layer 111 and a first transparent electrode layer 112. The first transparent electrode layer 112 is disposed on top of the first metal electrode layer 111, and the P-type base doped layer 12 is disposed on top of the first transparent electrode layer 112. This structure, through the first metal electrode layer 111 and the first transparent electrode layer 112, can improve charge collection efficiency, thereby increasing the fill factor and stability of the tandem solar cell.

[0054] In one embodiment, referring to FIG. 1 , a specific embodiment of a tandem solar cell provided in an embodiment of the present application, the surface electrode layer 26 includes a second transparent electrode layer 261 and a second metal electrode layer 262. The second transparent electrode layer 261 is disposed on top of the buffer layer 25, and the second metal electrode layer 262 is disposed on top of the second transparent electrode layer 261. This structure, through the second metal electrode layer 262 and the second transparent electrode layer 261, can improve charge collection efficiency, thereby increasing the fill factor and stability of the tandem solar cell.

[0055] In one embodiment, referring to FIG. 1 , a specific embodiment of a tandem solar cell provided in an embodiment of the present application is shown. The tandem solar cell further includes an anti-reflection layer 27, which is disposed on the top surface of the surface electrode layer 26, specifically on the top surface of the second metal electrode layer 262. This structure, through the anti-reflection layer 27, can enhance the tandem solar cell's absorption rate of sunlight and its operational stability.

[0056] In one embodiment, as shown in Figure 1, a crystalline silicon bottom cell 1 and a perovskite top cell 2 are arranged in series. In this structure, the crystalline silicon bottom cell 1 absorbs infrared light that the perovskite top cell 2 cannot utilize, converting ultraviolet light into visible light or near-infrared light, improving the light absorption performance of the tandem solar cell and, in turn, increasing the photoelectric conversion efficiency.

[0057] Referring to Figure 1, the specific structure of the stacked solar cell provided in the embodiment of the present application is as follows from bottom to top: a first metal electrode layer 111, a first transparent electrode layer 112, a P-type base doping layer 12, a base bottom passivation layer 13, a textured silicon substrate 14, a base surface passivation layer 15, an N-type base doping layer 16, a tunneling layer 17, a hole transport layer 21, a perovskite absorption layer 22, a perovskite passivation layer 23, an electron transport layer 24, a buffer layer 25, a second transparent electrode layer 261, a second metal electrode layer 262, and an anti-reflection layer 27. The preparation method of the stacked solar cell is described in detail. The steps for making the stacked solar cell are as follows:

[0058] Step 1: a substrate bottom passivation layer 13 and a P-type substrate doping layer 12 are sequentially formed on the bottom surface of the textured silicon substrate 14 , and a substrate surface passivation layer 15 and an N-type substrate doping layer 16 are sequentially formed on the top surface of the textured silicon substrate 14 .

[0059] Step 2: Prepare the first transparent electrode layer 112. Optionally, magnetron sputtering is used. Place the sample in a magnetron sputtering device, set up an ITO (Indium Tin Oxide) target, and control the power between 50W and 200W. Specifically, in this embodiment, the controlled power is 60W, the run time is 1.5 hours, and the film thickness is 100nm.

[0060] Step 3: Prepare the first metal electrode layer 111. Optionally, the prepared substrate sample is placed on a mask plate and placed in a chamber of an evaporation machine using an evaporation method. The evaporation vacuum is 5×10 -5 -2×10 -4 Pa, the evaporation temperature is 500-2000 ° C, and the evaporation rate is 0.1-5 Å / S. Specifically, in the embodiment of the present application, the evaporation vacuum is 2×10 -4 Pa, the evaporation voltage was adjusted to the evaporation temperature, the evaporation rate was controlled at 2.5Å / S, and silver was evaporated onto the film with a thickness of 200nm.

[0061] Step 4: Form a tunneling layer 17 on the surface of the N-type base doped layer 16. Optionally, tunneling layer 17 can be formed using atomic force microdeposition, magnetron sputtering, or wet chemical methods. Specifically, in this embodiment, magnetron sputtering is used. The sample is placed on a mask and then in a magnetron sputtering device with a controlled power of 60 W, a run time of 1 hour, and a film thickness of 40 nm.

[0062] Step 5: Prepare a hole transport layer 21 on the surface of the tunneling layer 17. The hole transport layer 21 can be at least one of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), poly-3-hexylthiophene (P3HT), nickel oxide (NiOx), molybdenum trioxide (MoO3), cuprous iodide (CuI), and cuprous thiocyanate (CuSCN).

[0063] Alternatively, a spin coating method can be used to evenly coat the hole transport layer 21 dispersion on the surface of the tunneling layer 17 at a spin coating speed of 1000-5000 rpm for 10-100 seconds. After the spin coating is completed, an annealing operation is performed at a temperature of 300°C-600°C for 10-50 minutes.

[0064] Optionally, a magnetron sputtering method may be used, and the prepared substrate is placed in a magnetron sputtering device with a controlled power of 30W-90W.

[0065] In this embodiment, a spin coating method can be used. The substrate is treated in a UV-Ozone cleaner for 15 minutes. A hole transport layer 21 dispersion is prepared by weighing 0.05 mol of NiOx powder and dissolving it in 1 ml of ultrapure water. Ultrasonic vibration is then applied for 20 minutes. The hole transport layer 21 dispersion is evenly applied to the surface of the sample. The spin coating speed is set to 2000 rpm, the spin coating time is 40 seconds, and the solution volume is 100 μl. After spin coating, an annealing operation is performed at 450°C for 30 minutes, with a thickness of approximately 20 nm.

[0066] Step 6: Prepare the perovskite absorption layer 22. Specifically, referring to FIG2 , the embodiment of the present application provides a method for preparing the perovskite absorption layer 22 by gradient co-evaporation, which specifically includes the following steps:

[0067] S1. Provide a textured substrate 100. Specifically, the textured substrate 100 is formed by combining the first metal electrode layer 111, the first transparent electrode layer 112, the P-type substrate doping layer 12, the substrate bottom passivation layer 13, the textured silicon substrate 14, the substrate surface passivation layer 15, the N-type substrate doping layer 16, the tunneling layer 17, and the hole transport layer 21.

[0068] S2. Prepare a mixed film 200 on the velvet substrate 100 by an evaporation method. The mixed film 200 includes lead iodide and cesium bromide. The evaporation rate of lead iodide is kept at a constant increasing rate during the coating process, and the content of lead iodide increases gradually from the buried bottom surface to the top surface of the mixed film 200. The evaporation rate of cesium bromide is kept at a constant decreasing rate during the coating process, and the content of cesium bromide decreases gradually from the buried bottom surface to the top surface of the mixed film 200.

[0069] Optionally, the evaporation rate of lead iodide is in the range of 0-10A / s, the evaporation rate of cesium bromide is in the range of 0-10A / s, the total evaporation time is controlled between 0-10000s, and the thickness of the formed mixed film 200 is between 200nm-800nm. In the traditional two-step preparation process, the evaporation rate of lead iodide and cesium bromide is maintained at a constant value throughout the coating process. However, in an embodiment of the present application, the evaporation rate of lead iodide and cesium bromide maintains a constant acceleration or deceleration throughout the coating process until the set maximum rate value or minimum rate value is reached. During the coating process, the rate ratio between lead iodide and cesium bromide is between 10:1 and 2:1.

[0070] Please refer to FIG3 . In an embodiment of the present application, the maximum evaporation rate of lead iodide is 8 A / s, and the maximum evaporation rate of cesium bromide is 0.8 A / s. The total evaporation time is controlled between 1000 s, and the thickness of the formed mixed film 200 is 440 nm. The evaporation rate of lead iodide maintains a constant acceleration rate throughout the evaporation process, and its constant acceleration rate is 0.008 A / s, that is, from 0 A / s at the beginning of evaporation, it increases gradually to 8 A / s at the end of coating. The evaporation rate of cesium bromide maintains a constant deceleration rate throughout the evaporation process, and its constant deceleration rate is -0.0008 A / s, that is, from 0.8 A / s at the beginning of evaporation, it decreases gradually to 0 A / s at the end of coating. During the coating process, the rate ratio between lead iodide and cesium bromide is controlled at 10:1.

[0071] S3, prepare ammonium salt precursor solution. Optionally, the ammonium salt precursor solution is prepared by dissolving ABX3 structure perovskite with an organic solvent. Wherein, in the ABX3 structure perovskite, the A position is an organic cation, including CH3NH3 + (MA + ), NH2CH=NH2 + (FA + ), CH3CH2NH3 + or Cs + At least one of; B position is a metal cation, including Pb 2+ 、Sn 2+ At least one of; X is a halogen anion, including F - 、Cl - Br - , I - The organic solvent includes at least one of ethanol, isopropanol, methanol, dimethylformamide (DMF), g-butyrolactone (GBL), dimethyl sulfoxide (DMSO) and N,N-dimethylacetamide.

[0072] Optionally, potassium iodide amidine, potassium bromide amidine, and an additive such as potassium chloride ammonium are dissolved in an organic solvent in a stoichiometric ratio, wherein the ratio of potassium iodide amidine to potassium bromide amidine is between 10:1 and 1:10; the ratio of the additive is between 0-50%; and the concentration of the ammonium salt precursor solution is controlled between 0.5M and 2M. Specifically, in an embodiment of the present application, the ratio of potassium iodide amidine to potassium bromide amidine can be 1:4.7; the additive is potassium chloride ammonium, and its addition ratio can be 10%wt; and the concentration of the ammonium salt precursor solution can be 1M.

[0073] S4. Applying an ammonium salt precursor solution to the surface of the mixed film 200 to form the perovskite absorption layer 22. Optionally, the ammonium salt precursor solution is applied to the surface of the mixed film 200 by spin coating at a spin coating speed of 1200 rpm to 6000 rpm for a spin coating time of 20 s to 120 s. After the spin coating is completed, annealing is performed at an annealing temperature of 50° C. to 150° C. for a spin coating time of 5 min to 40 min.

[0074] Specifically, in the embodiment of the present application, the spin coating speed may be 5000 rpm, the spin coating time may be 30 s, the annealing temperature may be 150° C., and the annealing time may be 10 min.

[0075] Step 7: Prepare a perovskite passivation layer 23. The perovskite passivation layer 23 may be propylenediamine iodide, including but not limited to at least one of propylenediamine bromide (PDADBr), butylammonium chloride (BACl), butylammonium bromide (BABr), butylammonium iodide (BAI), N,N-dimethyl-1,3-propylenediamine hydrochloride (DMePDADCl), and dodecanediamine bromide (DDDADBr); or magnesium fluoride, including but not limited to at least one of lithium fluoride (LiF) and sodium fluoride (NaF).

[0076] Optionally, propylene diamine iodide is evaporated onto the surface of the perovskite absorption layer 22 by evaporation, and the evaporation vacuum is 1Pa-5×10 -4 Pa, the evaporation temperature is 50℃-400℃, and the evaporation rate is 0.05Å / S-1Å / S. After the evaporation is completed, the annealing operation is performed, the annealing temperature is 0-150℃, and the annealing time is 0-30min.

[0077] Alternatively, a spin coating method can be used to prepare a passivation layer dispersion and evenly coat the surface of the perovskite absorption layer 22. Propylene diamine iodine is dissolved in an organic solvent including but not limited to methanol, ethanol, or isopropanol, ultrasonically dissolved, and spin-coated. The concentration of propylene diamine iodine is 0.1 mg / ml-6 mg / ml, the ultrasonic time is 0-30 minutes, the spin coating speed is 1000 rpm-7000 rpm, and the spin coating time is 20 seconds-120 seconds. After the spin coating is completed, an annealing operation is performed at an annealing temperature of 40°C-160°C and an annealing time of 5 minutes-40 minutes.

[0078] Optionally, the passivation layer dispersion can be sprayed onto the surface of the perovskite absorption layer 22 by spraying at a rate of 0-100 cm / s. After spraying, annealing is performed at a temperature of 20° C.-170° C. for a time of 0-30 min.

[0079] Specifically, the embodiment of the present application can adopt the evaporation method to prepare the perovskite passivation layer 23. Weigh 3 mg of propylene diamine iodine and place it in a crucible, place the substrate sample on the mask, and place it in the evaporation chamber. Wait for the evaporation vacuum to be 2×10 -4 Pa, the evaporation voltage was adjusted to the evaporation temperature, the evaporation rate was controlled at 0.1Å / S, and propylene diamine iodide was evaporated onto the layer film with a thickness of 4nm. After the completion, the annealing table temperature was set to 100℃ and annealing operation was performed for 8 minutes.

[0080] Step 8: Prepare the electron transport layer 24. The electron transport layer 24 is zinc oxide (ZnO), tin dioxide (SnO2), titanium dioxide (TiO2), [6,6]-phenyl C61 butyric acid methyl ester (PC 61 BM), carbon 60 (C 60 ), at least one of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP).

[0081] Optionally, the electron transport layer 24 dispersion can be evenly coated on the surface of the perovskite passivation layer 23 by spin coating, with a spin coating speed of 500 rpm-4000 rpm and a spin coating time of 10 s-80 s.

[0082] Optionally, the electron transport layer 24 material may be evaporated onto the surface of the perovskite passivation layer 23 by evaporation, and the evaporation vacuum degree is 5×10 -5 Pa-5×10 -4 Pa, the evaporation temperature is 100℃-400℃, and the evaporation rate is 0.05Å / S-1Å / S.

[0083] Specifically, the embodiment of the present application can adopt the evaporation method to prepare the electron transport layer 24. Specifically, the substrate sample is placed on the mask and placed in the evaporation chamber. The vacuum degree of the evaporation is 1×10 -4 Pa, the evaporation voltage was adjusted to the evaporation temperature, and the evaporation rate was controlled at 0.1Å / S. 60 Evaporated onto the film with a thickness of 20nm.

[0084] Step 9: Prepare a buffer layer 25. The buffer layer 25 is made of at least one of zinc oxide (ZnO), tin dioxide (SnO2), and titanium dioxide (TiO2). The thickness of the buffer layer 25 can range from 0 to 30 nm.

[0085] Optionally, the electron transport layer 24 material can be deposited onto the surface of the electron transport layer 24 using an atomic deposition method, with a deposition vacuum of 0-1×10 4 Pa, the deposition pipeline temperature is between 50℃-150℃, and the deposition chamber temperature is between 40℃-150℃.

[0086] Optionally, the modification layer material of the electron transport layer 24 can be evaporated onto the surface of the electron transport layer 24 by evaporation method, and the evaporation vacuum degree is 6×10 -5 Pa-4×10 -4 Pa, the evaporation temperature is 100℃-500℃, and the evaporation rate is 0.05Å / S-1Å / S.

[0087] Specifically, the embodiment of the present application can adopt the atomic accumulation deposition method, and the vacuum degree of the atomic accumulation deposition equipment is set to 0.5×10 4 Pa, the deposition channel temperature is between 60 ° C, the deposition chamber temperature is 70 ° C, and SnO2 is evaporated onto the layer film with a thickness of 15 nm.

[0088] Step 10: Prepare the second transparent electrode layer 261. Optionally, the transparent electrode material can be sputtered onto the surface of the buffer layer 25 by magnetron sputtering, with the power controlled at 30W-200W. Alternatively, the transparent electrode material can be evaporated onto the surface of the buffer layer 25 by evaporation, with the evaporation vacuum degree at 1×10 -5 Pa-5×10 -4 Pa, the evaporation temperature is 1000℃-2000℃, and the evaporation rate is 0.05Å / S-3Å / S.

[0089] Specifically, the embodiment of the present application can adopt a magnetron sputtering method, which is similar to the preparation method of preparing the first transparent electrode layer 112 in step 2, setting an IZO (Indium Zinc Oxide) target, controlling the power to 50W, the operating time to 1h, and the film thickness to 100nm.

[0090] Step 11: Prepare the second metal electrode layer 262. The process is similar to preparing the first metal electrode layer 111, with the exception of the mask. The thickness is 100 nm. The second metal electrode layer 262 is made of at least one of silver (Ag), gold (Au), copper (Cu), aluminum (Al), and carbon (C).

[0091] Step 12: Prepare the anti-reflection layer 27. Optionally, the anti-reflection layer 27 can be prepared by magnetron sputtering or evaporation. Specifically, the method for preparing the anti-reflection layer 27 in the embodiment of the present application is similar to the method for preparing the perovskite passivation layer 23. The evaporation rate is controlled at 2 Å / s, and magnesium fluoride is evaporated onto the film to a thickness of 100 nm. The anti-reflection layer 27 can be at least one of magnesium fluoride, lithium fluoride (LiF), sodium fluoride (NaF), and silicon oxide (SiO2).

[0092] The first transparent electrode layer 112 and the second transparent electrode layer 261 are made of at least one of indium tin oxide (ITO), indium zinc oxide (IZO), and aluminum zinc oxide (AZO). The thickness of the hole transport layer 21, perovskite absorption layer 22, electron transport layer 24, second transparent electrode layer 261, second metal electrode layer 262, and anti-reflection layer 27 can range from 1 nm to 600 nm.

[0093] In order to verify the method for preparing the perovskite absorption layer 22 by gradient co-evaporation and the performance of the stacked solar cell provided in the embodiments of the present application, the present application provides three comparative examples for comparison and demonstration.

[0094] Comparative Example 1 provides a stacked solar cell prepared based on a traditional two-step method. The difference between the preparation method of Comparative Example 1 and the preparation method of the embodiment of the present application lies in step six. The perovskite absorption layer 22 provided in Comparative Example 1 is prepared by a two-step method based on a traditional evaporation solution. The first step is to use gradient co-evaporation on a velvet substrate 100 to prepare a mixed film 200; the second step uses binary co-evaporation, wherein the evaporation rate of lead iodide is kept constant at 4A / s, and the evaporation rate of cesium bromide is kept constant at 0.4A / s. The total evaporation time is controlled at 1000s, and the thickness of the formed mixed film 200 is 440nm. During the coating process, the rate ratio between lead iodide and cesium bromide is controlled at 10:1. The relationship curve between the evaporation rate of lead iodide and the evaporation rate of cesium bromide and time is shown in Figure 4.

[0095] Comparative Example 2 provides a stacked solar cell prepared under different evaporation rate conditions. The difference between the preparation method of Comparative Example 2 and the preparation method of the embodiment of the present application lies in step six. The preparation conditions of the perovskite absorption layer 22 provided in Comparative Example 2 are: the maximum evaporation rate of lead iodide is 8A / s, and the evaporation rate of lead iodide maintains a constant growth rate throughout the coating process, with a constant growth rate value of 0.008A / s, gradually increasing from 0A / s at the beginning of evaporation to 8A / s at the end of coating; cesium bromide maintains a constant evaporation rate, and its value is controlled at 0.4A / s. The relationship curve between the evaporation rate of lead iodide and the evaporation rate of cesium bromide and time is shown in Figure 5.

[0096] Comparative Example 3 provides a stacked solar cell prepared under another different evaporation rate condition. The difference between the preparation method of Comparative Example 3 and the preparation method of the embodiment of the present application lies in step six. The preparation conditions of the perovskite absorption layer 22 provided in Comparative Example 3 are as follows: the maximum evaporation rate of lead iodide is 8A / s, and the evaporation rate of lead iodide maintains a constant deceleration during the entire coating process, and the constant deceleration value is -0.008A / s, that is, it gradually decreases from 8A / s at the beginning of evaporation to 0A / s at the end of coating; the maximum evaporation rate of cesium bromide is 0.8A / s, and the evaporation rate of cesium bromide maintains a constant acceleration during the entire coating process, and the constant acceleration value is 0.0008A / s, that is, it gradually increases from 0A / s at the beginning of evaporation to 0.8A / s at the end of coating. The relationship curve between the evaporation rate of lead iodide and the evaporation rate of cesium bromide and time is shown in Figure 6.

[0097] The present embodiment was compared with three comparative examples. A solar simulator was used to perform a standard solar intensity calibration. 2 The stacked solar cell was subjected to a long-term IV test with the starting voltage set to 1.95V, the cut-off voltage set to 0V, and the range set to 100mA. The test results are shown in the following table.

[0098]

[0099] From the comparison of the above tables we can see that:

[0100] 1. In Comparative Example 1, the lead iodide and cesium bromide of the mixed film 200 prepared by the traditional co-evaporation method are evenly distributed in the film. When reacting with the ammonium salt precursor solution, the lead iodide on its upper surface can react completely, while the lead iodide on its buried bottom surface cannot react completely because it cannot directly contact. These residual lead iodides will cause a large number of defects in the formed perovskite absorption layer 22, thereby reducing the efficiency of the stacked solar cell. The stacked solar cell provided in the embodiment of the present application has a higher open circuit voltage, short circuit current and photoelectric conversion efficiency than the comparative example 1 because of its higher quality perovskite absorption layer 22; moreover, since there is no residual lead iodide, the attenuation rate of the stacked solar cell provided in the embodiment of the present application is also much lower than that of the comparative example 1, and has good stability.

[0101] 2. In Comparative Example 2, the evaporation rate of cesium bromide remained constant, and the evaporation rate of lead iodide remained consistent with that of the present embodiment. The performance of the tandem solar cell provided in Comparative Example 2 is similar to that of the tandem solar cell provided in the present embodiment. This is because the distribution of lead iodide in Comparative Example 2 is similar to that in the present embodiment. The gradient distribution of lead iodide can both promote the formation of a high-quality perovskite absorber layer 22 without lead iodide residue.

[0102] 3. In Comparative Example 3, the evaporation rate of lead iodide maintains a constant deceleration during the entire coating process, and the evaporation rate of cesium bromide maintains a constant acceleration during the entire coating process. The content of lead iodide is large on the buried bottom surface of the mixed film 200, but small on the upper surface, resulting in a large amount of lead iodide residue on the buried bottom surface of the perovskite absorption layer 22 formed therein. The quality of the perovskite absorption layer 22 is extremely low. The performance of the stacked solar cell provided by Comparative Example 3 is far lower than that of the embodiments of the present application, Comparative Example 1 and Comparative Example 2.

[0103] Based on the above description, the method for preparing the perovskite absorption layer 22 by gradient co-evaporation and the stacked solar cell provided in the embodiment of the present application have at least the following beneficial effects: the embodiment of the present application adjusts the evaporation rate of lead iodide and cesium bromide by gradient, and the content of lead iodide increases gradually from the buried bottom surface to the upper surface of the mixed film 200, and the content of cesium bromide decreases gradually from the buried bottom surface to the upper surface of the mixed film 200. In this way, the lead iodide and the ammonium salt precursor solution can react more completely, reducing the residual lead iodide on the buried bottom surface of the mixed film 200, thereby forming a high-quality and low-defect-density perovskite absorption layer 22, thereby improving the performance of the stacked solar cell.

[0104] The above are merely optional embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for preparing a perovskite absorption layer by gradient co-evaporation, characterized in that: Includes steps: providing a suede base; A mixed film is prepared on the velvet substrate by an evaporation method; wherein the mixed film includes lead iodide and cesium bromide, the evaporation rate of the lead iodide maintains a constant increasing rate during the coating process, and the content of the lead iodide increases gradually from the buried bottom surface to the upper surface of the mixed film; the evaporation rate of the cesium bromide maintains a constant decreasing rate during the coating process, and the content of the cesium bromide decreases gradually from the buried bottom surface to the upper surface of the mixed film; preparing an ammonium salt precursor solution; The ammonium salt precursor solution is coated on the surface of the mixed film to prepare a perovskite absorption layer.

2. The method for preparing a perovskite absorber layer by gradient co-evaporation according to claim 1, characterized in that: During the coating process, the ratio of the evaporation rate of the lead iodide to the evaporation rate of the cesium bromide is a constant value, and the constant value is between 10:1 and 2:

1.

3. The method for preparing a perovskite absorber layer by gradient co-evaporation according to claim 1, characterized in that: The evaporation rate of the lead iodide maintains a constant increasing rate between 0-10A / s, and the constant increasing rate of the lead iodide is between 0.001A / s-0.01A / s; the evaporation rate of the cesium bromide maintains a constant decreasing rate between 0A / s-10A / s, and the constant decreasing rate of the cesium bromide is between -0.01A / s-0A / s.

4. The method for preparing a perovskite absorption layer by gradient co-evaporation according to claim 1, characterized in that: In the step of preparing the ammonium salt precursor solution: the ammonium salt precursor solution is prepared by dissolving the perovskite with ABX3 structure in an organic solvent.

5. The method for preparing a perovskite absorber layer by gradient co-evaporation as claimed in claim 4, characterized in that: In the ABX3 structured perovskite, the A position is an organic cation, including CH3NH3 + (MA + ), NH2CH=NH2 + (FA + )、CH3CH2NH3 + or Cs + At least one of; B position is a metal cation, including Pb 2+ Sn 2+ At least one of; X is a halogen anion, including F - , Cl - Br - ,I - At least one of .

6. The method for preparing a perovskite absorber layer by gradient co-evaporation according to claim 4, characterized in that: The organic solvent includes at least one of ethanol, isopropanol, methanol, dimethylformamide (DMF), G-butyrolactone (GBL), dimethyl sulfoxide (DMSO) and N,N-dimethylacetamide.

7. The method for preparing a perovskite absorption layer by gradient co-evaporation according to any one of claims 1 to 6, characterized in that: In the step of coating the ammonium salt precursor solution on the surface of the mixed film to obtain the perovskite absorption layer: coating the ammonium salt precursor solution on the surface of the mixed film by spin coating; and performing annealing after the spin coating.

8. A laminated solar cell, characterized in that: include: A crystalline silicon bottom cell, comprising a base electrode layer, a P-type base doping layer arranged on the top surface of the base electrode layer, a base bottom surface passivation layer arranged on the top surface of the P-type base doping layer, a textured silicon substrate arranged on the top surface of the base bottom surface passivation layer, a base surface passivation layer arranged on the top surface of the textured silicon substrate, an N-type base doping layer arranged on the top surface of the base surface passivation layer, and a tunneling layer arranged on the top surface of the N-type base doping layer; A perovskite top cell, comprising a hole transport layer disposed on the top surface of the tunneling layer, a perovskite absorption layer disposed on the top surface of the hole transport layer, a perovskite passivation layer disposed on the top surface of the perovskite absorption layer, an electron transport layer disposed on the top surface of the perovskite passivation layer, a buffer layer disposed on the top surface of the electron transport layer, and a surface electrode layer disposed on the top surface of the buffer layer; Wherein, the perovskite absorption layer is prepared by the method for preparing the perovskite absorption layer by gradient co-evaporation as described in any one of claims 1 to 7.

9. The tandem solar cell according to claim 8, characterized in that: The base electrode layer includes a first metal electrode layer and a first transparent electrode layer arranged on the top surface of the first metal electrode layer; the P-type base doping layer is arranged on the top surface of the first transparent electrode layer.

10. The tandem solar cell according to claim 9, wherein: The surface electrode layer includes a second transparent electrode layer disposed on the top surface of the buffer layer and a second metal electrode layer disposed on the top surface of the second transparent electrode layer.

11. The tandem solar cell according to claim 10, characterized in that: The first transparent electrode layer and the second transparent electrode layer are at least one of indium tin oxide (ITO), indium zinc oxide (IZO), and aluminum zinc oxide (AZO).

12. The tandem solar cell according to claim 10, wherein: The second metal electrode layer is at least one of silver (Ag), gold (Au), copper (Cu), aluminum (Al), and carbon (C).

13. The tandem solar cell according to claim 8, wherein: The stacked solar cell further comprises an anti-reflection layer arranged on the top surface of the surface electrode layer.

14. The tandem solar cell according to claim 13, wherein: The anti-reflection layer is at least one of magnesium fluoride, lithium fluoride (LiF), sodium fluoride (NaF), and silicon oxide (SiO2).

15. The tandem solar cell according to claim 8, wherein: The perovskite passivation layer is at least one of propylenediamine iodide, propylenediamine bromide (PDADBr), butylammonium chloride (BACl), butylammonium bromide (BABr), butylammonium iodide (BAI), N,N-dimethyl-1,3-propylenediamine hydrochloride (DMePDADCl), and dodecanediaminium bromide (DDDADBr); or, the perovskite passivation layer is at least one of magnesium fluoride, lithium fluoride (LiF), and sodium fluoride (NaF).

16. The tandem solar cell according to claim 8, wherein: The electron transport layer is zinc oxide (ZnO), tin dioxide (SnO2), titanium dioxide (TiO2), [6,6]-phenyl C61 butyric acid methyl ester (PC 61 BM), carbon 60 (C 60 ), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP).

17. The tandem solar cell according to claim 8, wherein: The buffer layer is at least one of zinc oxide (ZnO), tin dioxide (SnO2), and titanium dioxide (TiO2).

18. The tandem solar cell according to claim 8, wherein: The crystalline silicon bottom cell and the perovskite top cell are arranged in series.

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