Perovskite solar cells and their fabrication methods

Abstract

This application provides a perovskite solar cell, comprising, from bottom to top, a transparent conductive electrode, an electron transport layer, a heterostructure perovskite layer, a hole transport layer, and a back electrode. The positions of the electron transport layer and the hole transport layer are interchangeable. The heterostructure perovskite layer comprises a host perovskite layer and a cesium-based perovskite layer covering the surface of the host perovskite layer. This application also provides a method for fabricating a perovskite solar cell.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and in particular to a perovskite solar cell and its fabrication method. Background Technology

[0002] With the rapid development of the new energy field, solar cells have been widely used in military, aerospace, industrial, commercial, agricultural, and communications fields. Perovskite solar cells, with their advantages of high photoelectric conversion efficiency, simple manufacturing process, and low production and material costs, have gradually become a hot topic in next-generation solar cell research.

[0003] Due to the significant advancements in perovskite solar cells, higher demands have been placed on their photoelectric conversion efficiency and long-term stability. However, existing perovskite thin films inevitably exhibit various intrinsic defects during fabrication, affecting the stability of perovskite solar cells. Therefore, the long-term stability of current perovskite solar cells still needs improvement. Summary of the Invention

[0004] This application is made in view of the above-mentioned issues, and its purpose is to provide a perovskite solar cell with high photoelectric conversion efficiency and long-term stability.

[0005] To achieve the above objectives, this application provides a perovskite solar cell and a method for its fabrication.

[0006] The first aspect of this application provides a perovskite solar cell, which includes, from bottom to top, a transparent conductive electrode, an electron transport layer, a heterogeneous perovskite layer, a hole transport layer, and a back electrode, wherein the positions of the electron transport layer and the hole transport layer are interchangeable, and the heterogeneous perovskite layer includes a host perovskite layer and a cesium-based perovskite layer covering the surface of the host perovskite layer.

[0007] Therefore, by forming a cesium-based perovskite layer on the surface of the host perovskite layer, this application can suppress the migration of A-site ions in the host perovskite layer (molecular formula ABX3), reduce the loss of A-site ions, and thus improve the long-term stability of perovskite solar cells.

[0008] In any embodiment, the molecular formula of the cesium-based perovskite layer material is CsBX3, wherein B is an inorganic, organic, or organic-inorganic mixed cation, optionally Pb. 2+ and Sn 2+ At least one of them, and optionally Pb 2+ X is an inorganic, organic, or mixed organic-inorganic anion, optionally at least one of a halide anion and a carboxylate anion, and further optionally Br. - Or I- .

[0009] In any embodiment, the thickness of the cesium-based perovskite layer on the upper and lower surfaces of the host perovskite layer is 1-30 nm, optionally 3-10 nm. When the thickness of the cesium-based perovskite layer on the upper and lower surfaces of the host perovskite layer is within the given range, the long-term stability of the perovskite solar cell can be further improved.

[0010] In any embodiment, the material of the host perovskite layer has the molecular formula ABX3, wherein A comprises inorganic, organic, or mixed organic-inorganic cations, optionally including formamidinium cations, methylamine cations, and optionally Cs. + Optionally, it may further include formamidinium cation or methylamine cation; B is an inorganic, organic, or mixed organic-inorganic cation, optionally Pb. 2+ and Sn 2+ At least one of them, and optionally Pb 2+ X is an inorganic, organic, or mixed organic-inorganic anion, optionally at least one of a halide anion and a carboxylate anion, and further optionally Br. - Or I - .

[0011] In any embodiment, the thickness of the main perovskite layer is 200-1000 nm.

[0012] In any embodiment, the ratio of the thickness of the host perovskite layer to the thickness of the cesium-based perovskite layer on the upper and lower surfaces of the host perovskite layer is 16.7-500. When the ratio of the thickness of the host perovskite layer to the thickness of the cesium-based perovskite layer on the upper and lower surfaces of the host perovskite layer is within the given range, the long-term stability of the perovskite solar cell can be further improved.

[0013] A second aspect of this application also provides a method for preparing a perovskite solar cell, comprising the following steps:

[0014] Step 1: Provide a transparent conductive electrode;

[0015] Step 2: Fabricate an electron transport layer on the transparent conductive electrode;

[0016] Step 3: First, a cesium-based perovskite underlayer is prepared on the electron transport layer. Then, a host perovskite layer is prepared on the cesium-based perovskite underlayer. Finally, a cesium-based perovskite surface layer is prepared on the host perovskite layer to obtain a heterogeneous perovskite layer.

[0017] Step 4: Prepare a hole transport layer on the heterogeneous perovskite layer;

[0018] Step 5: Fabricate a back electrode on the hole transport layer to obtain a perovskite solar cell.

[0019] The steps for preparing the electron transport layer and the steps for preparing the hole transport layer can be interchanged, and

[0020] The perovskite solar cell includes, from bottom to top, a transparent conductive electrode, an electron transport layer, a heterogeneous perovskite layer, a hole transport layer, and a back electrode. The positions of the electron transport layer and the hole transport layer are interchangeable. The heterogeneous perovskite layer includes a main perovskite layer and a cesium-based perovskite layer covering the surface of the main perovskite layer.

[0021] Therefore, the method described in this application can be used to prepare the perovskite solar cell described in this application using conventional preparation steps and at low cost.

[0022] In any embodiment, in step 3, the heterogeneous perovskite layer is prepared by vapor deposition.

[0023] In any embodiment, the molecular formula of the cesium-based perovskite layer material is CsBX3, wherein B is an inorganic, organic, or organic-inorganic mixed cation, optionally Pb. 2+ and Sn 2+ At least one of them, and optionally Pb 2+ X is an inorganic, organic, or mixed organic-inorganic anion, optionally at least one of a halide anion and a carboxylate anion, and further optionally Br. - Or I - .

[0024] In any embodiment, the thickness of the cesium-based perovskite layer on the upper and lower surfaces of the main perovskite layer is 1-30 nm, optionally 3-10 nm.

[0025] In any embodiment, the material of the host perovskite layer has the molecular formula ABX3, wherein A comprises inorganic, organic, or mixed organic-inorganic cations, optionally including formamidinium cations, methylamine cations, and optionally Cs. + Optionally, it may further include formamidinium cation or methylamine cation; B is an inorganic, organic, or mixed organic-inorganic cation, optionally Pb. 2+ and Sn 2+ At least one of them, and optionally Pb 2+ X is an inorganic, organic, or mixed organic-inorganic anion, optionally at least one of a halide anion and a carboxylate anion, and further optionally Br. - Or I - .

[0026] In any embodiment, the thickness of the main perovskite layer is 200-1000 nm.

[0027] In any embodiment, the ratio of the thickness of the main perovskite layer to the thickness of the cesium-based perovskite layer on the upper and lower surfaces of the main perovskite layer is 16.7-500. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a perovskite solar cell according to one embodiment of this application.

[0029] Figure 2 This is a schematic diagram illustrating the principle of how the cesium-based perovskite layer of the perovskite solar cell in one embodiment of this application suppresses the migration of A-site ions in the host perovskite layer. Detailed Implementation

[0030] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the perovskite solar cell and its fabrication method of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of essentially identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0031] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0032] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0033] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0034] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0035] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0036] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0037] Perovskite solar cells have gradually become a hot topic in next-generation solar cell research due to their advantages such as high photoelectric conversion efficiency, simple fabrication process, and low production and material costs. However, during the preparation of perovskite (molecular formula ABX3) thin films, intrinsic defects such as vacancy defects, interstitial defects, and antisite defects inevitably occur to varying degrees. These defects lead to the migration, escape, and degradation of component ions, especially A-site methylamine and formamidinium ions. This phenomenon will quickly destroy the perovskite structure, thereby causing the solar cell device to fail.

[0038] Extensive experiments have shown that forming a cesium-based perovskite layer on the surface of the main perovskite layer can suppress ion migration, reduce A-site losses, and thus improve the long-term stability of the battery device.

[0039] In one embodiment of this application, a perovskite solar cell is proposed, comprising, from bottom to top, a transparent conductive electrode, an electron transport layer, a heterogeneous perovskite layer, a hole transport layer, and a back electrode. The positions of the electron transport layer and the hole transport layer are interchangeable. The heterogeneous perovskite layer comprises a main perovskite layer and a cesium-based perovskite layer covering the surface of the main perovskite layer.

[0040] like Figure 1 As shown, the perovskite solar cell of this application includes a transparent conductive electrode, an electron transport layer, a heterogeneous perovskite layer, a hole transport layer, and a back electrode arranged sequentially from bottom to top. The positions of the electron transport layer and the hole transport layer can be interchanged, and the heterogeneous perovskite layer includes a main perovskite layer and a cesium-based perovskite layer covering the surface of the main perovskite layer.

[0041] Although the mechanism is not yet clear, this application forms a cesium-based perovskite layer on the surface of the host perovskite layer. The cesium-based perovskite can transform into a β-phase structure at room temperature. The β-phase structure has high radiation stability, high thermodynamic stability, high carrier migration characteristics, and wide bandgap to suppress carrier recombination. It can suppress the migration of A-site ions in the host perovskite layer and reduce the loss of A-site ions. By utilizing the self-healing function of perovskite, the intrinsic stability of the host perovskite layer is improved. In addition, the cesium-based perovskite has good water and oxygen stability and a higher internal defect formation energy, which can further improve the long-term stability of perovskite solar cells.

[0042] like Figure 2 As shown, when the host perovskite layer (bulk phase) is Alpha phase FAPbI3 and the cesium-based perovskite layer (surface) is Beta phase (i.e. β phase) CsPbI3, the Pb-I octahedral rotation in the cesium-based perovskite layer causes lattice deformation, which reduces the diffusion channels of A-site ions (in this embodiment, A-site ions are FA cations, where FA represents formamidinium cations) in the host perovskite layer and increases the migration barrier. This can suppress the migration of A-site ions in the host perovskite layer, improve the thermodynamic stability of the perovskite layer, and inhibit the degradation of the battery device.

[0043] In some embodiments, the molecular formula of the cesium-based perovskite layer material is CsBX3, wherein B is an inorganic, organic, or organic-inorganic mixed cation, optionally Pb. 2+ and Sn 2+ At least one of them, and optionally Pb 2+ X is an inorganic, organic, or mixed organic-inorganic anion, optionally at least one of a halide anion and a carboxylate anion, and further optionally Br. - Or I - .

[0044] In some implementations, the cesium-based perovskite layer is on the upper and lower surfaces of the host perovskite layer.

[0045] In some embodiments, the thickness of the cesium-based perovskite layer on both the upper and lower surfaces of the host perovskite layer is 1-30 nm, optionally 3-10 nm.

[0046] When the thickness of the cesium-based perovskite layer on the upper and lower surfaces of the main perovskite layer is within the given range, the long-term stability of the perovskite solar cell can be further improved.

[0047] In some embodiments, the material of the host perovskite layer has the molecular formula ABX3, wherein A comprises an inorganic or organic or mixed organic-inorganic cation, optionally comprising a formamidinium cation, a methylamine cation, and optionally Cs. + Optionally, it may further include formamidinium cation or methylamine cation; B is an inorganic, organic, or mixed organic-inorganic cation, optionally Pb. 2+ and Sn 2+ At least one of them, and optionally Pb 2+ X is an inorganic, organic, or mixed organic-inorganic anion, optionally at least one of a halide anion and a carboxylate anion, and further optionally Br. - Or I - .

[0048] In some implementations, the thickness of the main perovskite layer is 200-1000 nm.

[0049] In some embodiments, the ratio of the thickness of the host perovskite layer to the thickness of the cesium-based perovskite layer on the upper and lower surfaces of the host perovskite layer is 16.7-500.

[0050] In some implementations, the cesium-based perovskite layer has the same thickness on both the upper and lower surfaces of the host perovskite layer.

[0051] In this application, the ratio of the thickness of the main perovskite layer to the thickness of the cesium-based perovskite layer on the upper and lower surfaces of the main perovskite layer refers to the ratio of the thickness of the main perovskite layer to the thickness of the cesium-based perovskite layer on the upper surface of the main perovskite layer or the ratio of the thickness of the main perovskite layer to the thickness of the cesium-based perovskite layer on the lower surface of the main perovskite layer.

[0052] When the ratio of the thickness of the main perovskite layer to the thickness of the cesium-based perovskite layer on the upper and lower surfaces of the main perovskite layer is within the given range, the long-term stability of the perovskite solar cell can be further improved.

[0053] In some embodiments, the material of the transparent conductive electrode includes glass and a transparent conductive oxide on the glass, wherein the transparent conductive oxide is selected from fluorine-doped tin oxide (FTO), indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), boron-doped zinc oxide (BZO), indium zinc oxide (IZO), etc.

[0054] In some embodiments, the transparent conductive electrode comprises 0.1-3 mm thick glass and 50-1000 nm thick transparent conductive oxide.

[0055] In some embodiments, the electron transport layer is made of at least one of the following materials and their derivatives, or materials obtained by doping or passivation: [6,6]-phenyl-C 61 methyl butyrate (PC) 61 BM), [6,6]-phenyl-C 71 methyl butyrate (PC) 71 BM), fullerene C60 (C60), fullerene C70 (C70), tin dioxide (SnO2), zinc oxide (ZnO), titanium dioxide (TiO2), etc.

[0056] In some implementations, the thickness of the electron transport layer is 5-200 nm.

[0057] In some embodiments, the hole transport layer is made of at least one of the following materials and their derivatives, or materials obtained by doping or passivation: poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD), poly(3-hexylthiophene) (P3HT), triphenylamine with a triphenylene core (H101), 3,4-ethylenedioxythiophene-methoxytriphenylamine (EDOT-OMeTPA), N-(4-aniline)carbazole-spirobifluorene (CzPAF-SBF), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS), polythiophene, nickel oxide (NiOx), molybdenum oxide (MoO3), cuprous iodide (CuI), cuprous oxide (Cu2O), etc.

[0058] In some implementations, the thickness of the hole transport layer is 5-300 nm.

[0059] In some embodiments, the material of the back electrode is an organic, inorganic, or organic-inorganic mixed conductive material, optionally Ag, Cu, C, Au, Al, ITO, AZO, BZO, IZO, or a carbon derivative.

[0060] In some implementations, the thickness of the back electrode is 10-1000 nm.

[0061] In some implementations, corresponding decorative layers can be inserted between the above layers.

[0062] In one embodiment of this application, a method for preparing a perovskite solar cell is provided, comprising the following steps:

[0063] Step 1: Provide a transparent conductive electrode;

[0064] Step 2: Fabricate an electron transport layer on a transparent conductive electrode;

[0065] Step 3: First, a cesium-based perovskite underlayer is prepared on the electron transport layer. Then, a host perovskite layer is prepared on the cesium-based perovskite underlayer. Finally, a cesium-based perovskite surface layer is prepared on the host perovskite layer to obtain a heterogeneous perovskite layer.

[0066] Step 4: Prepare a hole transport layer on the heterogeneous perovskite layer;

[0067] Step 5: Fabricate the back electrode on the hole transport layer to obtain a perovskite solar cell.

[0068] The steps for preparing the electron transport layer and the steps for preparing the hole transport layer are interchangeable, and

[0069] A perovskite solar cell includes, from bottom to top, a transparent conductive electrode, an electron transport layer, a heterogeneous perovskite layer, a hole transport layer, and a back electrode. The positions of the electron transport layer and the hole transport layer can be interchanged. The heterogeneous perovskite layer includes a main perovskite layer and a cesium-based perovskite layer covering the surface of the main perovskite layer.

[0070] The method described in this application allows for the fabrication of the perovskite solar cell of this application using conventional fabrication steps at low cost.

[0071] In some embodiments, in step 3, at least one of the following methods is used to prepare the heterogeneous perovskite layer: chemical bath deposition, electrochemical deposition, chemical vapor deposition, physical epitaxial growth, thermal evaporation co-evaporation, atomic layer deposition, precursor liquid spin coating, precursor liquid slot coating, precursor liquid scraping, mechanical pressing, etc.; optionally, thermal evaporation and precursor liquid coating (spin coating) methods are used to prepare the heterogeneous perovskite layer.

[0072] In some embodiments, in step 3, the heterogeneous perovskite layer is prepared by vapor deposition.

[0073] In some embodiments, the molecular formula of the cesium-based perovskite layer material is CsBX3, wherein B is an inorganic, organic, or organic-inorganic mixed cation, optionally Pb. 2+ and Sn 2+ At least one of them, and optionally Pb 2+X is an inorganic, organic, or mixed organic-inorganic anion, optionally at least one of a halide anion and a carboxylate anion, and further optionally Br. - Or I - .

[0074] In some embodiments, the thickness of the cesium-based perovskite layer on both the upper and lower surfaces of the host perovskite layer is 1-30 nm, optionally 3-10 nm.

[0075] In some embodiments, the material of the host perovskite layer has the molecular formula ABX3, wherein A comprises an inorganic or organic or mixed organic-inorganic cation, optionally comprising a formamidinium cation, a methylamine cation, and optionally Cs. + Optionally, it may further include formamidinium cation or methylamine cation; B is an inorganic, organic, or mixed organic-inorganic cation, optionally Pb. 2+ and Sn 2+ At least one of them, and optionally Pb 2+ X is an inorganic, organic, or mixed organic-inorganic anion, optionally at least one of a halide anion and a carboxylate anion, and further optionally Br. - Or I - .

[0076] In some implementations, the thickness of the main perovskite layer is 200-1000 nm.

[0077] In some embodiments, the ratio of the thickness of the host perovskite layer to the thickness of the cesium-based perovskite layer on the upper and lower surfaces of the host perovskite layer is 16.7-500.

[0078] In some embodiments, the hole transport layer, electron transport layer, and electrodes can be fabricated using methods conventional in the art.

[0079] Example

[0080] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0081] Example 1

[0082] Step 1: Clean the surface of an FTO conductive glass with dimensions of 2.0cm×2.0cm×0.2cm (FTO thickness of 500nm) twice with acetone and isopropanol, immerse it in deionized water and sonicate for 10 minutes, then dry it in a forced-air drying oven and place it in a glove box (N2 atmosphere).

[0083] Step 2: Using a spin coater (LEBO EZ6-S), a 3% by weight SnO2 nanocolloid aqueous solution was spin-coated onto the dried FTO conductive glass at a speed of 5000 rpm. Then, it was heated at 150℃ for 15 min on a constant temperature stage to obtain a 30 nm electron transport layer.

[0084] Step 3: In a vacuum coating machine, at 5×10 -4 Under vacuum conditions of Pa, on the electron transport layer A 5 nm thick CsPbI3 substrate was deposited using a high-rate evaporation process, with the evaporation source being a CsPbI3 single crystal. Then, the evaporation source was replaced with a FAPbI3 single crystal, and the CsPbI3 substrate was deposited using a high-rate evaporation process. A 500 nm thick FAPbI3 host perovskite layer was deposited at a specific evaporation rate; finally, the evaporation source was replaced with a CsPbI3 single crystal, and evaporation was continued on the FAPbI3 host perovskite layer at a specific evaporation rate. A CsPbI3 surface layer with a thickness of 5 nm was deposited at a certain rate to obtain a heterogeneous perovskite layer.

[0085] Step 4: Using a spin coater (LEBO EZ6-S), spin coat a 73 mg / mL chlorobenzene solution of Spiro-OMeTAD onto the heterostructured perovskite layer at a speed of 5000 rpm to obtain a hole transport layer with a thickness of 150 nm.

[0086] Step 5: In a vacuum coating machine, at 5×10 -4 Under vacuum conditions of Pa, on the hole transport layer... The back electrode was obtained by evaporating Ag with a thickness of 80 nm at a certain rate.

[0087] The perovskite solar cell described in this application is obtained through the above steps.

[0088] Examples 2-7

[0089] The fabrication of the perovskite solar cell was generally carried out in accordance with Example 1, except that in step 3, the thicknesses of the CsPbI3 bottom layer and the CsPbI3 surface layer were 1 nm, 3 nm, 10 nm, 30 nm, 0.5 nm and 35 nm, respectively.

[0090] Example 8

[0091] The fabrication of the perovskite solar cell was generally carried out in accordance with Example 1, except that in step 3, CsPbBr3 single crystal was used as the evaporation source to deposit the CsPbBr3 underlayer and CsPbBr3 surface layer.

[0092] Example 9

[0093] The fabrication of the perovskite solar cell was generally carried out in accordance with Example 1, except that in step 3, a MAPbI3 host perovskite layer was deposited by MAPbI3 single crystal evaporation.

[0094] Example 10

[0095] The fabrication of the perovskite solar cell was generally carried out in accordance with Example 1, except that steps 2 and 4 were interchanged, so that the perovskite solar cell included FTO conductive glass, Spiro-OMeTAD hole transport layer, heterogeneous perovskite layer, SnO2 electron transport layer and Ag back electrode arranged in sequence.

[0096] Example 11

[0097] The fabrication of the perovskite solar cell was generally carried out in accordance with Example 1, except that in step 3, the thickness of the CsPbI3 bottom layer and the CsPbI3 surface layer was 20 nm, and the thickness of the FAPbI3 main perovskite layer was 1000 nm.

[0098] Example 12

[0099] The fabrication of the perovskite solar cell was generally carried out in accordance with Example 1, except that in step 3, the thickness of the CsPbI3 bottom layer and the CsPbI3 surface layer was 8 nm, and the thickness of the FAPbI3 main perovskite layer was 200 nm.

[0100] Comparative Example 1

[0101] The fabrication of the perovskite solar cell was generally carried out according to Example 1, except that step 3 was performed in a vacuum coating machine at a temperature of 5 × 10⁻⁶. -4 Under vacuum conditions of Pa, on the electron transport layer A 500 nm thick FAPbI3 perovskite layer was deposited at a certain rate.

[0102] Test methods

[0103] 1. Photovoltaic conversion efficiency of perovskite solar cells

[0104] In an atmospheric environment, AM1.5 G standard light source was used to simulate sunlight. A four-channel digital source meter (Keithley 2440) was used to measure the current-voltage characteristic curve of the battery under the illumination of the light source, and the open circuit voltage Voc, short circuit current density Jsc, and fill factor FF of the battery were obtained. The energy conversion efficiency Eff of the battery was then calculated.

[0105] Energy conversion efficiency is calculated as follows:

[0106] Eff = Pout / Popp

[0107] =Voc×Jsc×(Vmpp×Jmpp) / (Voc×Jsc)

[0108] =Voc×Jsc×FF

[0109] Where Pout, Popp, Vmpp, and Jmpp are the battery's operating output power, incident light power, battery's maximum power point voltage, and maximum power point current, respectively.

[0110] 2. Stability performance of perovskite solar cells

[0111] The battery was placed in an environment with a relative humidity (RH) of 75-80% and an ambient temperature of 25-30℃ for 800 hours without being protected from light. Its photoelectric conversion efficiency was measured, and the ratio of the battery efficiency after 800 hours to the initial efficiency was calculated as a parameter for battery stability.

[0112] The perovskite solar cells obtained in the above embodiments and comparative examples were tested according to the above process, and the specific values ​​are shown in Table 1.

[0113]

[0114] As shown in Table 1, by forming a cesium-based perovskite layer on the surface of the main perovskite layer, the photoelectric conversion efficiency and cell stability of the perovskite solar cells in all the above embodiments are higher than those of the comparative perovskite solar cells.

[0115] Comparing Examples 1 to 7, when the thickness of the cesium-based perovskite layer is 1-30 nm, the photoelectric conversion efficiency and cell stability of the perovskite solar cell can be significantly improved; when the thickness of the cesium-based perovskite layer is 3-10 nm, the photoelectric conversion efficiency and cell stability of the perovskite solar cell can be further improved.

[0116] Comparing Examples 1 and 8-10, the heterogeneous perovskite layer described in this application exhibits good compatibility with different cesium-based perovskite layer materials, host perovskite layer materials, and both formal and inverted perovskite solar cells.

[0117] Comparing Examples 1-7 and 11-12, when the ratio of the thickness of the main perovskite layer to the thickness of the cesium-based perovskite layer on the upper and lower surfaces of the main perovskite layer is 16.7-500, the cell stability of the perovskite solar cell can be further improved.

[0118] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A perovskite solar cell, comprising, from bottom to top, a transparent conductive electrode, an electron transport layer, a heterostructure perovskite layer, a hole transport layer, and a back electrode, wherein the positions of the electron transport layer and the hole transport layer are interchangeable, wherein, The heterogeneous perovskite layer includes a host perovskite layer and a cesium-based perovskite layer covering the surface of the host perovskite layer. The ratio of the thickness of the main perovskite layer to the thickness of the cesium-based perovskite layer on the upper and lower surfaces of the main perovskite layer is 16.7-500.

2. The perovskite solar cell according to claim 1, wherein, The molecular formula of the cesium-based perovskite layer is CsBX3, where B is an inorganic, organic, or organic-inorganic mixed cation, and X is an inorganic, organic, or organic-inorganic mixed anion.

3. The perovskite solar cell according to claim 2, wherein, B is Pb 2+ and Sn 2+ At least one of them.

4. The perovskite solar cell according to claim 2 or 3, wherein, B is Pb 2+ .

5. The perovskite solar cell according to claim 2 or 3, wherein, X is at least one of a halide anion and a carboxylate anion.

6. The perovskite solar cell according to claim 2 or 3, wherein, X is Br - Or I - .

7. The perovskite solar cell according to claim 1 or 2, wherein, The thickness of the cesium-based perovskite layer on both the upper and lower surfaces of the main perovskite layer is 1-30 nm.

8. The perovskite solar cell according to claim 1 or 2, wherein, The thickness of the cesium-based perovskite layer on both the upper and lower surfaces of the main perovskite layer is 3-10 nm.

9. The perovskite solar cell according to claim 1 or 2, wherein, The molecular formula of the main perovskite layer is ABX3, where A contains inorganic or organic or organic-inorganic mixed cations, B is inorganic or organic or organic-inorganic mixed cations, and X is inorganic or organic or organic-inorganic mixed anions.

10. The perovskite solar cell according to claim 9, wherein, A contains formamidinium cation, methylamine cation, and optional Cs. + .

11. The perovskite solar cell according to claim 9, wherein, A contains formamidin cations or methylamine cations.

12. The perovskite solar cell according to claim 9, wherein, B is Pb 2+ and Sn 2+ At least one of them.

13. The perovskite solar cell according to claim 9, wherein, B is Pb 2+ .

14. The perovskite solar cell according to claim 9, wherein, X is at least one of a halide anion and a carboxylate anion.

15. The perovskite solar cell according to claim 9, wherein, X is Br - Or I - .

16. The perovskite solar cell according to any one of claims 1, 2, 3 or 10-14, wherein, The thickness of the main perovskite layer is 200-1000 nm.

17. A method for preparing a perovskite solar cell according to any one of claims 1-16, comprising the following steps: Step 1: Provide a transparent conductive electrode; Step 2: Fabricate an electron transport layer on the transparent conductive electrode; Step 3: First, a cesium-based perovskite underlayer is prepared on the electron transport layer. Then, a host perovskite layer is prepared on the cesium-based perovskite underlayer. Finally, a cesium-based perovskite surface layer is prepared on the host perovskite layer to obtain a heterogeneous perovskite layer. Step 4: Prepare a hole transport layer on the heterogeneous perovskite layer; Step 5: Fabricate a back electrode on the hole transport layer to obtain a perovskite solar cell. The steps for preparing the electron transport layer and the steps for preparing the hole transport layer can be interchanged, and The perovskite solar cell includes, from bottom to top, a transparent conductive electrode, an electron transport layer, a heterogeneous perovskite layer, a hole transport layer, and a back electrode. The positions of the electron transport layer and the hole transport layer are interchangeable. The heterogeneous perovskite layer includes a main perovskite layer and a cesium-based perovskite layer covering the surface of the main perovskite layer.

18. The method according to claim 17, wherein, In step 3, the heterogeneous perovskite layer is prepared by vapor deposition.

19. The method according to claim 17 or 18, wherein, The molecular formula of the cesium-based perovskite layer is CsBX3, where B is an inorganic, organic, or organic-inorganic mixed cation, and X is an inorganic, organic, or organic-inorganic mixed anion.

20. The method according to claim 19, wherein, B is Pb 2+ and Sn 2+ At least one of them.

21. The method according to claim 19, wherein, B is Pb 2+ .

22. The method according to claim 19, wherein, X is at least one of a halide anion and a carboxylate anion.

23. The method according to claim 19, wherein, X is Br - Or I - .

24. The method according to claim 17 or 18, wherein, The thickness of the cesium-based perovskite layer on both the upper and lower surfaces of the main perovskite layer is 1-30 nm.

25. The method according to claim 17 or 18, wherein, The thickness of the cesium-based perovskite layer on both the upper and lower surfaces of the main perovskite layer is 3-10 nm.

26. The method according to claim 17 or 18, wherein, The molecular formula of the main perovskite layer is ABX3, where A contains inorganic or organic or organic-inorganic mixed cations, B is inorganic or organic or organic-inorganic mixed cations, and X is inorganic or organic or organic-inorganic mixed anions.

27. The method according to claim 26, wherein, A contains formamidinium cation, methylamine cation, and optional Cs. + .

28. The method according to claim 26, wherein, A contains formamidin cations or methylamine cations.

29. The method according to claim 26, wherein, B is Pb 2+ and Sn 2+ At least one of them.

30. The method of claim 26, wherein, B is Pb 2+ .

31. The method according to claim 26, wherein, X is at least one of a halide anion and a carboxylate anion.

32. The method according to claim 26, wherein, X is Br - Or I - .

33. The method according to claim 17 or 18, wherein, The thickness of the main perovskite layer is 200-1000 nm.

34. The method according to claim 17 or 18, wherein, The ratio of the thickness of the main perovskite layer to the thickness of the cesium-based perovskite layer on the upper and lower surfaces of the main perovskite layer is 16.7-500.

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