Transition layer, laminated structure comprising same and perovskite solar cell

Abstract

The invention belongs to the photovoltaic field, and particularly relates to a transition layer, a laminated structure containing the transition layer and a perovskite solar cell. The transition layer comprises fluorine-containing resin and MXene, and the MXene is distributed in a mass concentration gradient mode in the thickness direction of the transition layer. According to the invention, hydrophobicity of fluorine-containing resin and chemical stability of MXene are combined, hygrothermal stability of the perovskite solar cell is improved, stress concentration of a perovskite / C60 interface is relieved through gradient modulus design, and defect passivation and carrier transport optimization are realized at the same time.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaics and relates to a transition layer and a stacked structure containing the same, as well as perovskite solar cells. Background Technology

[0002] In perovskite solar cells, the stress concentration at the interface between the perovskite layer and the C60 electron transport layer severely restricts the long-term stability of the device. The soft lattice properties of perovskite materials are prone to distortion under high temperature and light exposure, while the rigid structure of C60 leads to a mismatch in the coefficient of thermal expansion (CTE), causing lattice stress accumulation, ultimately resulting in cracking of the perovskite layer and a decrease in device efficiency. Although traditional polymer interface layers (such as PMMA and PDMS) can provide some stress buffering, their modulus is limited, failing to achieve a continuous modulus transition from perovskite (modulus 10-20 GPa) to C60 (modulus 4-6 GPa). Therefore, there is an urgent need to find a transition layer that can alleviate the stress concentration at the interface between the perovskite layer and the electron transport layer. Summary of the Invention

[0003] This invention addresses the aforementioned problems in existing technologies by proposing a transition layer, a stacked structure containing the transition layer, and a perovskite solar cell. The transition layer comprises a fluorinated resin and MXene, wherein the MXene exhibits a mass concentration gradient distribution along the directions of the perovskite layer and the electron transport layer. This invention combines the hydrophobicity of the fluorinated resin with the chemical stability of MXene, improving the damp-heat stability of the perovskite solar cell. Through gradient modulus design, it alleviates stress concentration at the C60 interface of the perovskite / electron transport layer, while simultaneously achieving defect passivation and optimized carrier transport.

[0004] Specifically, the present invention provides a transition layer between a perovskite layer and an electron transport layer, the transition layer comprising a fluorinated resin and MXene, wherein the MXene is distributed in a mass concentration gradient along the thickness direction of the transition layer.

[0005] In one or more embodiments, the thickness of the transition layer is 2 to 5 nm.

[0006] In one or more embodiments, the MXene is selected from Ti3C2T. x V2CT x Nb2CT x Ti2CT x and Ti3CNT x One or more of them.

[0007] In one or more embodiments, the fluorinated resin is selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, and perfluoroalkoxy resins.

[0008] In one or more embodiments, the MXene mass concentration on the side of the transition layer closer to the perovskite layer is greater than the MXene mass concentration on the side of the transition layer closer to the electron transport layer.

[0009] In one or more embodiments, the transition layer comprises, in the thickness direction, a first fluorinated resin / MXene composite layer to an Nth fluorinated resin / MXene composite layer and an N+1th fluorinated resin layer, where N is an integer ≥ 2.

[0010] In one or more embodiments, the transition layer comprises, in the thickness direction, a first fluorinated resin / MXene composite layer to an (N+1)th fluorinated resin / MXene composite layer, where N is an integer ≥ 2.

[0011] In one or more embodiments, the first to Nth fluorinated resin / MXene composite layers comprise fluorinated resin and MXene.

[0012] In one or more embodiments, the ratio of the mass of MXene to the total mass of MXene and fluorinated resin in the first to the Nth fluorinated resin / MXene composite layers is independently 1 to 30 wt%.

[0013] In one or more embodiments, the ratio of the mass of MXene to the total mass of MXene and fluorinated resin in the first fluorinated resin / MXene composite layer is 15 to 30 wt%.

[0014] In one or more embodiments, the ratio of the mass of MXene to the total mass of MXene and fluorinated resin in the Nth fluorinated resin / MXene composite layer is 1 to 5 wt%.

[0015] In one or more implementations, N is 2.

[0016] In one or more embodiments, the N+1 fluorinated resin layer comprises a fluorinated resin but does not contain MXene.

[0017] In one or more embodiments, the N+1th fluorinated resin / MXene composite layer comprises fluorinated resin and MXene, wherein the ratio of the mass of MXene to the total mass of MXene and fluorinated resin in the N+1th fluorinated resin / MXene composite layer is >0 and ≤1 wt%.

[0018] In one or more embodiments, a surface in the transition layer with a higher MXene mass concentration is configured to contact the perovskite layer.

[0019] In one or more embodiments, in the transition layer, the average mass fraction of MXene in the transition layer is 10 to 40 wt% from the surface with a higher MXene mass concentration to a depth of 1 nm from that surface; and in the transition layer, the average mass fraction of MXene in the transition layer is 0 to 5 wt% from the surface with a lower MXene mass concentration to a depth of 1 nm from that surface.

[0020] The present invention also provides a method for preparing a transition layer as described in any embodiment herein, the method comprising: (1) Coating the first coating liquid to the Nth coating liquid in sequence, where N is an integer ≥ 2, to obtain a coating precursor containing MXene; the first coating liquid to the Nth coating liquid contain MXene and fluorinated resin; the ratio of the mass of MXene to the total mass of MXene and fluorinated resin in the first coating liquid to the Nth coating liquid decreases in sequence. (2) A resin coating liquid is applied to the surface of the MXene-containing coating precursor to obtain a transition layer precursor, wherein the resin coating liquid contains fluorinated resin and does not contain MXene; or an N+1 coating liquid is applied to the surface of the MXene-containing coating precursor to obtain a transition layer precursor, wherein the N+1 coating liquid contains MXene and fluorinated resin, and the ratio of the mass of MXene in the N+1 coating liquid to the total mass of MXene and fluorinated resin is less than the ratio of the mass of MXene in the N coating liquid to the total mass of MXene and fluorinated resin. (3) Anneal the precursor of the transition layer to obtain the transition layer.

[0021] In one or more embodiments, the solvents in the first to Nth coating solutions are independently selected from one or both of isopropanol and chlorobenzene.

[0022] In one or more embodiments, the ratio of the mass of MXene to the total mass of MXene and fluorinated resin in the first to Nth coating solutions is independently 1 to 30 wt%.

[0023] In one or more embodiments, the ratio of the mass of MXene in the first coating solution to the total mass of MXene and fluorinated resin is 15 to 30 wt%.

[0024] In one or more embodiments, the ratio of the mass of MXene in the Nth coating solution to the total mass of MXene and fluorinated resin is 1 to 5 wt%.

[0025] In one or more embodiments, the ratio of the mass of MXene in the N+1th coating solution to the total mass of MXene and fluorinated resin is >0 and ≤1 wt%.

[0026] In one or more embodiments, the total concentration of MXene and fluorinated resin in the first to Nth coating solutions is independently 0.5 to 2 mg / mL.

[0027] In one or more embodiments, the concentration of fluorinated resin in the resin coating solution is 0.5~1.9 mg / mL.

[0028] In one or more embodiments, the solvent in the resin coating solution is selected from one or both of chlorobenzene and isopropanol.

[0029] In one or more embodiments, the annealing temperature is 90°C to 120°C, and the annealing time is 10 to 30 minutes.

[0030] In one or more embodiments, N is 2, the ratio of the mass of MXene in the first coating solution to the total mass of MXene and fluorinated resin is 15 to 30 wt%, and the ratio of the mass of MXene in the second coating solution to the total mass of MXene and fluorinated resin is 1 to 5 wt%.

[0031] In one or more embodiments, the first coating liquid is applied by spin coating, with a spin coating speed of 2000~3000 rpm and a spin coating time of 10~30 s.

[0032] In one or more embodiments, the second to Nth coating liquids are applied by spin coating, wherein the spin coating speed is independently 1000 to 2000 rpm and the spin coating time is independently 10 to 30 s.

[0033] In one or more embodiments, the resin coating liquid is applied by spin coating, with a spin coating speed of 500~1000 rpm and a spin coating time of 10~30 s.

[0034] The present invention also provides a perovskite solar cell, wherein the perovskite solar cell comprises, in the thickness direction, a hole transport layer, a perovskite layer, a transition layer as described in any embodiment herein, and an electron transport layer in sequence.

[0035] In one or more embodiments, a surface in the transition layer with a higher MXene mass concentration is in contact with the perovskite layer.

[0036] In one or more embodiments, the electron transport layer is selected from one or more of C60 and C60 derivatives.

[0037] In one or more embodiments, the C60 derivative is selected from one or both of [6,6]-phenyl-C61-butyrate isomethyl ester and [6,6]-phenyl-C71-butyrate isomethyl ester.

[0038] The present invention also provides a stacked assembly comprising a perovskite cell and a crystalline silicon cell as described in any embodiment herein, wherein the perovskite cell is disposed above the crystalline silicon cell.

[0039] The present invention also provides the use of the transition layer described in any embodiment herein in perovskite solar cells.

[0040] The present invention also provides the use of the transition layer described in any embodiment of the present invention in alleviating stress concentration at the interface between the perovskite layer and the electron transport layer.

[0041] The present invention also provides the use of the transition layer described in any embodiment herein in improving the open-circuit voltage, fill factor, short-circuit current, photoelectric conversion efficiency and / or high-temperature operating stability of perovskite solar cells. Attached Figure Description

[0042] Figure 1 This is a structural diagram of a perovskite solar cell in some embodiments of the present invention. Detailed Implementation

[0043] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used herein are explained and defined in general terms below. Unless otherwise specified, all technical and scientific terms used herein have the common meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0044] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0045] In this document, the terms “contains,” “includes,” “containing,” and similar terms encompass the meanings of “basically composed of” and “composed of.” For example, when this document discloses “A contains B and C,” “A is basically composed of B and C” and “A is composed of B and C” should be considered as having been disclosed in this document.

[0046] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0047] Unless otherwise specified, percentages refer to mass percentages and proportions refer to mass ratios in this article.

[0048] In this article, the sum of the percentages of all components in the composition is 100%.

[0049] In this document, when describing embodiments or examples, it should be understood that it is not intended to limit the invention to those embodiments or examples. Rather, all alternatives, modifications, and equivalents of the methods and materials described herein are covered within the scope of this invention.

[0050] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0051] This invention provides a transition layer comprising a fluorinated resin and MXene, located between a perovskite layer and an electron transport layer. The MXene exhibits a mass concentration gradient distribution along the thickness direction of the transition layer. This invention's transition layer achieves a modulus gradient through the MXene mass concentration gradient, thereby alleviating stress concentration at the perovskite / electron transport layer interface, reducing grain boundary crack density, and thus effectively improving the photothermal stability of the perovskite solar cell. This invention utilizes the high conductivity of MXene (conductivity 10⁻⁶). 3 -10 4 The S / m) form a continuous conductive network, reducing carrier recombination, achieving defect passivation and optimized carrier transport, and improving the device fill factor (FF) and short-circuit current (J). sc This invention improves the hydrophobicity of perovskite solar cells and enhances photoelectric conversion efficiency (PCE). Furthermore, by combining the hydrophobicity of fluorinated resins with the chemical stability of MXene, this invention improves the damp-heat stability of perovskite solar cells while simultaneously achieving defect passivation and carrier transport optimization.

[0052] transition layer

[0053] The transition layer of the present invention comprises a fluorinated resin and MXene, wherein the MXene is distributed in a mass concentration gradient along the thickness direction of the transition layer.

[0054] In this invention, MXene is a class of two-dimensional inorganic compounds composed of transition metal carbides, nitrides, or carbonitrides with a thickness of several atomic layers. MXene materials exhibit metallic conductivity, such as Ti3C2T. x Its conductivity can reach 10 3 -10 4 The S / m ratio allows for the formation of a continuous conductive network within the transition layer of this invention, thereby reducing carrier recombination and improving the device fill factor, short-circuit current, and photoelectric conversion efficiency. The chemical formula of MXene material is M... m+1 X m T x(m = 1, 2, or 3), where M is a transition metal selected from one or more of Ti, Cr, Ta, Nb, Mo, Zr, V, and Hf; X is C and / or N; T represents a surface group, including one or more of -OH, -O, and -F; x represents the average number of MXene surface groups, and the value of x is usually between 0 and 2. The MXene material suitable for this invention can be selected from Ti3C2T. x V2CT x Nb2CT x Ti2CT x and Ti3CNT x One or more of these types of MXene materials can be used in the transition layer of this invention to adjust the modulus gradient and form a conductive network, thereby alleviating stress concentration at the C60 interface of the perovskite / electron transport layer and achieving defect passivation and carrier transport optimization.

[0055] In this invention, MXene itself has a high modulus (100~300 GPa). When the MXene content in the transition layer is low, it is difficult to form an effective modulus gradient adjustment, causing the overall modulus of the transition layer to approach the elastic modulus of fluoropolymers (e.g., the elastic modulus of PVDF is about 0.5~4 GPa). This prevents the formation of an effective gradient modulus transition with the perovskite layer (modulus 10~20 GPa) and C60 (modulus 4~6 GPa), resulting in limited relief of interfacial stress concentration and a tendency for perovskite layer cracking or interfacial delamination. Conversely, excessively high MXene content can cause a sudden increase in the local modulus of the transition layer (e.g., local modulus > 50 GPa), far exceeding the modulus range of perovskite and C60, disrupting the continuity of the gradient design. For example, if the MXene content in the transition layer near the C60 side is too high, the modulus of the transition layer may jump from 15 GPa to 80 GPa, creating a new stress interface within the transition layer and leading to interlayer cracking or delamination.

[0056] In this invention, the thickness of the transition layer is 2~5 nm, which can be 2 nm, 3 nm, 4 nm, or 5 nm.

[0057] In this invention, fluorinated resin is a type of thermoplastic resin containing fluorine atoms in its molecular structure. It possesses excellent water resistance, high and low temperature resistance, dielectric properties, chemical stability, weather resistance, non-flammability, non-stickiness, and a low coefficient of friction. In the structure of tandem perovskite solar cells, fluorinated resin can serve a dual function of physical barrier (hydrophobic film) and mechanical buffer (high elastic modulus). The fluorinated resin in this invention is selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), and perfluoroalkoxy resin (PFA). When used in the transition layer of this invention, these types of fluorinated resins can all provide physical barrier and mechanical buffering, alleviating stress concentration at the perovskite / electron transport layer C60 interface, achieving defect passivation and optimized carrier transport.

[0058] In some embodiments, the fluoropolymer is PVDF. PVDF is a highly non-reactive thermoplastic fluoropolymer with excellent properties such as anti-aging, chemical resistance, weather resistance, and UV radiation resistance. It can be used to make sealing rings, corrosion-resistant equipment, capacitors, etc. PVDF is hydrophobic. In some embodiments, the present invention uses PVDF as the matrix resin of the transition layer. This design has the following advantages: (1) The polar groups in the PVDF molecule, such as -CF2- and -CH2-, are adsorbed onto the surface of the electron transport layer through electrostatic interaction or hydrogen bonding to neutralize the charge at the defect sites; (2) PVDF has good flexibility (elastic modulus of about 0.5~4). (3) The side of the perovskite layer near the electron transport layer may have halogen vacancies or grain boundary defects due to incomplete crystallization of perovskite. The PVDF polymer chain can fill these micro-defects through the steric hindrance effect to form a smoother interface. (4) In this invention, the PVDF layer is a barrier layer. The hydrophobic fluorocarbon chain reduces the direct interaction between the polar solvent in the perovskite precursor solution and the electron transport layer, thus avoiding chemical corrosion of the electron transport layer. (5) PVDF has high hydrophobicity and can form a moisture barrier at the interface to prevent external water vapor from penetrating to the perovskite / C60 interface, delaying the moisture absorption and decomposition of perovskite, and improving the humid heat stability of perovskite solar cells by combining the chemical stability of MXene.

[0059] In this invention, the elastic modulus of the fluorinated resin can be 0.4~4 GPa. Fluorinated resins (e.g., PVDF, PTFE, PVF, and PFA) are polymer materials, and their elastic modulus is typically between 0.1 and 4 GPa. Specifically, the elastic modulus of PVDF is approximately 0.5~4 GPa; the elastic modulus of PTFE is approximately 0.4~0.8 GPa; the elastic modulus of PFA is approximately 0.4~0.6 GPa; and the elastic modulus of PVF is approximately 2.1~2.6 GPa. In this invention, the elastic modulus of the fluorinated resin can be 0.4 GPa, 0.5 GPa, 0.6 GPa, 0.7 GPa, 0.8 GPa, 0.9 GPa, 1.0 GPa, 1.1 GPa, 1.2 GPa, 1.3 GPa, 1.4 GPa, 1.5 GPa, 1.8 GPa, 2.0 GPa, 2.2 GPa, 2.5 GPa, 2.8 GPa, 3.0 GPa, 3.2 GPa, 3.5 GPa, 3.8 GPa, 4.0 GPa, or a range formed by any two of the above values ​​as endpoints.

[0060] The transition layer of the present invention comprises, in the thickness direction, a first fluorinated resin / MXene composite layer to an Nth fluorinated resin / MXene composite layer and an (N+1)th fluorinated resin layer, where N is an integer ≥ 2. For example, when N=2, the transition layer comprises, in the thickness direction, a first fluorinated resin / MXene composite layer, a second fluorinated resin / MXene composite layer, and a third fluorinated resin layer; when N=3, the transition layer comprises, in the thickness direction, a first fluorinated resin / MXene composite layer, a second fluorinated resin / MXene composite layer, a third fluorinated resin / MXene composite layer, and a fourth fluorinated resin layer; and so on.

[0061] In this invention, the first fluorinated resin / MXene composite layer to the Nth fluorinated resin / MXene composite layer contain fluorinated resin and MXene, or are composed of fluorinated resin and MXene.

[0062] In this invention, the ratio of the mass of MXene to the total mass of MXene and fluorinated resin in the first to the Nth fluorinated resin / MXene composite layers can be independently 1 to 30 wt%, for example 1 wt%, 2 wt%, 2.5 wt%, 3 wt%, 4 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, and 30 wt%.

[0063] In this invention, the ratio of the mass of MXene to the total mass of MXene and fluorinated resin in the first fluorinated resin / MXene composite layer is preferably 15 to 30 wt%, for example, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, or 30 wt%.

[0064] In this invention, the ratio of the mass of MXene to the total mass of MXene and fluorinated resin in the Nth fluorinated resin / MXene composite layer is preferably 1 to 5 wt%, for example, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, and 5 wt%.

[0065] In some embodiments, N is 2. In this case, in the first fluorinated resin / MXene composite layer, the ratio of the mass of MXene to the total mass of MXene and fluorinated resin is preferably 15-30 wt%, for example, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, or 30 wt%; in the second fluorinated resin / MXene composite layer, the ratio of the mass of MXene to the total mass of MXene and fluorinated resin is preferably 1-5 wt%, for example, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%.

[0066] In this invention, the fluorinated resin layer comprises a fluorinated resin but does not contain MXene. In some embodiments, the fluorinated resin layer is composed of a fluorinated resin.

[0067] In some embodiments, the fluoropolymer layer can be replaced by an (N+1)th fluoropolymer / MXene composite layer, i.e., the transition layer sequentially includes a first fluoropolymer / MXene composite layer to an (N+1)th fluoropolymer / MXene composite layer in the thickness direction, where N is an integer ≥ 2. The (N+1)th fluoropolymer / MXene composite layer comprises fluoropolymer and MXene. In the (N+1)th fluoropolymer / MXene composite layer, the ratio of the mass of MXene to the total mass of MXene and fluoropolymer is > 0 and ≤ 1 wt%, for example, 0.01 wt%, 0.1 wt%, 0.2 wt%, and 0.5 wt%.

[0068] This invention introduces MXene with a gradient mass concentration distribution into a fluoropolymer matrix to obtain a transition layer. The modulus of the transition layer lies between that of the perovskite layer and the electron transport layer, serving as a modulus transition and effectively alleviating the stress concentration problem at the perovskite-electron transport layer interface. Preferably, the transition layer comprises at least three layers; more preferably, the MXene content in each layer is controlled within the range described above, which can more effectively alleviate the stress concentration problem at the perovskite-electron transport layer interface.

[0069] In this invention, within the transition layer from a surface with a high MXene mass concentration to a depth of 1 nm from that surface, the average mass fraction of MXene in the transition layer can be 10~40 wt%, for example, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, or 40 wt%.

[0070] In this invention, the average mass fraction of MXene in the transition layer can be 0 to 5 wt% from a surface with a low MXene mass concentration to a depth of 1 nm from that surface, for example, 0 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, and 5 wt%.

[0071] This invention provides a method for preparing the transition layer of this invention, comprising the following steps: (1) Coating the first coating liquid to the Nth coating liquid in sequence, where N is an integer ≥ 2, to obtain a coating precursor containing MXene; the first coating liquid to the Nth coating liquid contain MXene and fluorinated resin; the ratio of the mass of MXene to the total mass of MXene and fluorinated resin in the first coating liquid to the Nth coating liquid decreases in sequence. (2) A resin coating liquid is coated on the surface of the MXene-containing coating precursor to obtain a transition layer precursor, wherein the resin coating liquid contains fluorinated resin and does not contain MXene; or a coating liquid is coated on the surface of the MXene-containing coating precursor for the N+1th time to obtain a transition layer precursor, wherein the N+1th coating liquid contains MXene and fluorinated resin, and the ratio of the mass of MXene in the N+1th coating liquid to the total mass of MXene and fluorinated resin is less than the ratio of the mass of MXene in the Nth coating liquid to the total mass of MXene and fluorinated resin. (3) Anneal the transition layer precursor to obtain the transition layer.

[0072] In this invention, the solvents in the first coating liquid to the Nth coating liquid can be independently selected from one or both of isopropanol and chlorobenzene.

[0073] In this invention, the ratio of the mass of MXene to the total mass of MXene and fluorinated resin in the first coating liquid to the Nth coating liquid can each be independently 1 to 30 wt%, for example 1 wt%, 2 wt%, 2.5 wt%, 3 wt%, 4 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, and 30 wt%.

[0074] In this invention, the ratio of the mass of MXene in the first coating liquid to the total mass of MXene and fluorinated resin is preferably 15-30 wt%, for example 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, or 30 wt%.

[0075] In this invention, the ratio of the mass of MXene in the Nth coating liquid to the total mass of MXene and fluorinated resin is preferably 1 to 5 wt%, for example, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, and 5 wt%.

[0076] In this invention, the ratio of the mass of MXene in the N+1 coating solution to the total mass of MXene and fluorinated resin is >0 and ≤1wt%, for example, 0.01 wt%, 0.1 wt%, 0.2 wt%, 0.5 wt%.

[0077] In this invention, the total concentration of MXene and fluorinated resin in the first to Nth coating solutions can each be independently 0.5~2 mg / mL, for example 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL, 1.0 mg / mL, 1.1 mg / mL, 1.2 mg / mL, 1.3 mg / mL, 1.4 mg / mL, 1.5 mg / mL, 1.6 mg / mL, 1.7 mg / mL, 1.8 mg / mL, and 1.9 mg / mL.

[0078] In this invention, the concentration of fluorinated resin in the resin coating solution can be 0.5~1.9 mg / mL, for example 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL, 1.0 mg / mL, 1.1 mg / mL, 1.2 mg / mL, 1.3 mg / mL, 1.4 mg / mL, 1.5 mg / mL, 1.6 mg / mL, 1.7 mg / mL, 1.8 mg / mL, and 1.9 mg / mL.

[0079] In this invention, the solvent in the resin coating liquid can be selected from one or both of chlorobenzene and isopropanol.

[0080] In this invention, the annealing temperature is 90℃~120℃, such as 90℃, 100℃, 110℃, 120℃; the annealing time is 10~30 min, such as 10 min, 15 min, 20 min, 25 min, 30 min.

[0081] In some preferred embodiments, N is 2, and the ratio of the mass of MXene in the first coating liquid to the total mass of MXene and fluorinated resin is 15-30 wt%, which can be 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, or 30 wt%; the ratio of the mass of MXene in the second coating liquid to the total mass of MXene and fluorinated resin is 1-5 wt%, which can be 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%.

[0082] In this invention, the first coating liquid can be applied by spin coating, and the spin coating speed can be 2000~3000 rpm, for example 2000 rpm, 2100 rpm, 2200 rpm, 2300 rpm, 2400 rpm, 2500 rpm, 2600 rpm, 2700 rpm, 2800 rpm, 2900 rpm, or 3000 rpm; the spin coating time can be 10~30 s, for example 10 s, 12 s, 15 s, 17 s, 18 s, 20 s, 22 s, 25 s, 28 s, or 30 s.

[0083] In this invention, the coating method for the second to the Nth coating liquid can be spin coating. The spin coating speed can be independently set to 1000~2000 rpm, for example, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm, or 2000 rpm. The spin coating time can be independently set to 10~30 s, for example, 10 s, 11 s, 12 s, 13 s, 14 s, 15 s, 16 s, 17 s, 18 s, 19 s, 20 s, 21 s, 22 s, 23 s, 24 s, 25 s, 26 s, 27 s, 28 s, 29 s, or 30 s.

[0084] In this invention, the resin coating liquid can be applied by spin coating, and the spin coating speed can be 500~1000 rpm, for example 500 rpm, 600 rpm, 700 rpm, 750 rpm, 800 rpm, 900 rpm, 1000 rpm; the spin coating time can be 10~30 s, for example 10 s, 11 s, 12 s, 13 s, 14 s, 15 s, 16 s, 17 s, 18 s, 19 s, 20 s, 21 s, 22 s, 23 s, 24 s, 25 s, 26 s, 27 s, 28 s, 29 s, 30 s.

[0085] Perovskite solar cells

[0086] This invention provides a perovskite solar cell incorporating a transition layer of this invention. In some embodiments, the perovskite solar cell sequentially comprises a hole transport layer, a perovskite layer, the transition layer of this invention, and an electron transport layer in the thickness direction. The surface of the transition layer with a higher MXene mass concentration is in contact with the perovskite layer. The elastic modulus of the transition layer is related to the content of MXene with a high elastic modulus; the elastic modulus of the surface with a higher MXene mass concentration is higher than that of the surface with a lower MXene concentration. Therefore, the elastic modulus of the perovskite layer, the transition layer, and the electron transport layer decreases sequentially, forming a modulus gradient, thereby reducing the risk of stress concentration and preventing cracking at the interfaces.

[0087] In this invention, the electron transport layer comprises one or more of C60 and C60 derivatives. The C60 derivative may be one or both of [6,6]-phenyl-C61-butyrate isomethyl ester (

[60] PCBM) and [6,6]-phenyl-C71-butyrate isomethyl ester (

[70] PCBM).

[0088] In this invention, the thickness of the electron transport layer can be 5~50 nm, such as 5 nm, 10 nm, 12 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, or 50 nm.

[0089] In this invention, the perovskite cell may include an inverted tandem perovskite solar cell.

[0090] In this invention, the inverted tandem perovskite solar cell may sequentially include a back electrode, a bottom cell, a tunneling layer, a hole transport layer, a perovskite layer, the transition layer of this invention, an electron transport layer, a transparent conductive substrate, an antireflection layer, and a top electrode. In some embodiments, the inverted tandem perovskite solar cell further includes a buffer layer located between the electron transport layer and the transparent conductive substrate.

[0091] Figure 1 Exemplary structures of perovskite solar cells incorporating the transition layer of the present invention are provided in some embodiments.

[0092] In this invention, the transparent conductive substrate can be selected from one or more transparent conductive oxides (TCOs), such as fluorine-doped tin oxide (FTO), indium zinc oxide (IZO), indium tin oxide (ITO), or flexible indium tin oxide (ITO), with a thickness of 20~100 nm, such as 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm.

[0093] In this invention, the tunneling layer can be one or more of the following: indium tin oxide, indium zinc oxide, cerium-doped indium oxide, tungsten-doped indium oxide, aluminum-doped zinc oxide, antimony-doped tin oxide, zirconium-doped indium oxide, gallium zinc-doped indium oxide, heavily doped n-silicon and p-silicon combination, and n-silicon combined with other p-type materials. The thickness is 20~200 nm, and can be 20 nm, 30 nm, 50 nm, 80 nm, 100 nm, 120 nm, 130 nm, 150 nm, 180 nm, or 200 nm.

[0094] In some implementations, a sputtering method is used to prepare the transparent conductive substrate and the tunneling layer.

[0095] In this invention, the antireflection layer can be MgF₂. x It can be one or two of LiF, with a thickness of 20~200 nm, which can be 20 nm, 50 nm, 80 nm, 100 nm, 110 nm, 120 nm, 130 nm, 150 nm, 180 nm, or 200 nm.

[0096] In this invention, the hole transport layer can be prepared by one or more methods selected from spin coating, blade coating, vapor deposition, printing, spraying, spray pyrolysis, and slot coating. The material used to prepare the hole transport layer is selected from one or more of metal oxides, single-molecule self-assembled materials containing phosphate groups, and single-molecule self-assembled materials containing carboxylic acid groups. The single-molecule self-assembled material containing phosphate groups can be selected from one or more of [4-(9H-carbazole-9-yl)ethyl]phosphoric acid (4PACz), [2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid (MeO-2PACz), (2-(9H-carbazole-9-yl)ethyl)phosphonic acid (2PACz), and [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid (Me-4PACz). The metal oxide can be NiO. x In this invention, the concentration of the material used to prepare the hole transport layer is 0.5~3 mg / mL, and can be 0.5 mg / mL, 0.75 mg / mL, 1.0 mg / mL, 1.2 mg / mL, 1.5 mg / mL, 1.8 mg / mL, 2 mg / mL, 2.2 mg / mL, 2.5 mg / mL, 2.8 mg / mL, or 3 mg / mL. The hole transport layer is prepared by annealing at 90℃~120℃ for 5~15 min, where the annealing temperature can be 90℃, 100℃, 110℃, or 120℃, and the annealing time can be 5 min, 8 min, 10 min, 12 min, or 15 min.

[0097] In this invention, the thickness of the hole transport layer can be 2~5 nm, such as 2 nm, 3 nm, 4 nm, or 5 nm.

[0098] In this invention, the perovskite layer of the perovskite solar cell has the chemical formula ABX3, wherein the A ion is a monovalent cation, including but not limited to Cs. + 、Rb + A monovalent cation or a mixture of monovalent cations, including methylamine ion and formamidinium ion; β ion is a divalent cation, including but not limited to Pb. 2+ Cu 2+ Zn 2+ Ga 2+ Sn 2+ and Ca 2+ The X ion is a divalent cation or a mixture of multiple divalent cations; the X ion is a monovalent anion, including but not limited to I. - ,Br - Cl - F - and SCN - It is a mixture of one or more monovalent anions.

[0099] In this invention, the concentration of the perovskite precursor solution for the perovskite solar cell can be 1~2 mol / mL, specifically 1.0 mol / mL, 1.1 mol / mL, 1.2 mol / mL, 1.3 mol / mL, 1.4 mol / mL, 1.5 mol / mL, 1.6 mol / mL, 1.7 mol / mL, 1.8 mol / mL, 1.9 mol / mL, or 2 mol / mL.

[0100] In this invention, the solvent in the perovskite precursor solution is selected from one or more of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), γ-butyrolactone (GBL), and N-methylpyrrolidone (NMF). In some embodiments, the organic solvent is selected from two of N,N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, and N-methylpyrrolidone, in which case the volume ratio of the two organic solvents is (3-5):1. For example, the organic solvent can be a mixture of N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of (3-5):1, where the volume ratio can be 3:1, 4:1, or 5:1; the organic solvent can also be a mixture of γ-butyrolactone and N-methylpyrrolidone in a volume ratio of (3-5):1, where the volume ratio can be 3:1, 4:1, or 5:1; the organic solvent can also be a mixture of N,N-dimethylformamide and N-methylpyrrolidone in a volume ratio of (3-5):1, where the volume ratio can be 3:1, 4:1, or 5:1.

[0101] In this invention, the thickness of the perovskite layer can be 400~700 nm, such as 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, or 700 nm.

[0102] In this invention, the perovskite layer is prepared by one or more of spin coating, blade coating, vapor deposition, printing, spraying, spray pyrolysis, and slot coating.

[0103] In some implementations, the perovskite layer is prepared by spin coating, which includes spin coating a perovskite precursor solution, adding an antisolvent, and annealing.

[0104] In some implementations, phenylethylamine hydroiodide (PEAI) can be added to the perovskite precursor solution to regulate crystallization. The concentration of PEAI in the perovskite precursor solution is 0.5–2 mg / mL, such as 0.5 mg / mL, 1 mg / mL, 1.5 mg / mL, or 2 mg / mL.

[0105] In some implementations, the spin coating speed of the perovskite precursor solution is 2000~4000 rpm, such as 2000 rpm, 2200 rpm, 2400 rpm, 2500 rpm, 2600 rpm, 2700 rpm, 2800 rpm, 2900 rpm, 3000 rpm, 3200 rpm, 3500 rpm, 3800 rpm, and 4000 rpm; the spin coating time is 30~50 s, such as 30 s, 35 s, 40 s, 45 s, and 50 s.

[0106] In some implementations, the antisolvent is selected from one or more of anisole, ethyl acetate, and chlorobenzene.

[0107] In this invention, the perovskite layer is prepared by annealing at 90℃~120℃ for 15~30 min. The annealing temperature can be 90℃, 100℃, 110℃, or 120℃, and the annealing time can be 15 min, 18 min, 20 min, 25 min, 28 min, or 30 min.

[0108] In this invention, the top electrode and the back electrode can be Ag, Cu or Au, and the thickness can be 100~400 nm, such as 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 350 nm, or 400 nm.

[0109] In this invention, the buffer layer can be selected from one or more of BCP, SnO2, Al2O3 and zirconium acetylacetonate, and the thickness can be 5~50 nm, such as 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, and 50 nm.

[0110] In this invention, the method for preparing an inverted tandem perovskite solar cell may include: Using crystalline silicon solar cells as the bottom cell and inverted perovskite solar cells as the top cell; An intrinsic amorphous silicon layer on the back side and an intrinsic amorphous silicon layer on the front side are prepared on both sides of an N-type silicon wafer. A p-type amorphous silicon layer is deposited on the back-side amorphous silicon layer; An n-type amorphous silicon layer is deposited on the front intrinsic amorphous silicon layer; A transparent conductive oxide is deposited on the surface of a p-type amorphous silicon layer; A back electrode is fabricated on a transparent conductive oxide surface; Deposit a tunneling layer on an n-type amorphous surface; Deposit a hole transport layer on the surface of the tunneling layer; Deposit a perovskite layer on the surface of the hole transport layer; Deposit a transition layer on the surface of the perovskite layer; An electron transport layer is deposited on the surface of the transition layer; A transparent conductive substrate and a top electrode are deposited on the surface of the electron transport layer to obtain an inverted tandem perovskite solar cell.

[0111] In some implementations, the method for fabricating inverted tandem perovskite solar cells further includes: first depositing a buffer layer on the surface of the electron transport layer, and then depositing a transparent conductive substrate and a top electrode on the surface of the buffer layer.

[0112] In some embodiments, the method for fabricating inverted tandem perovskite solar cells further includes: first depositing an antireflection layer on the surface of a transparent conductive substrate, and then depositing a back electrode on the surface of the antireflection layer.

[0113] In some implementations, the thickness of the N-type silicon wafer is 200~400 nm, such as 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 340 nm, 350 nm, 380 nm, and 400 nm.

[0114] In some implementations, intrinsic amorphous silicon, n-type amorphous silicon, and p-type amorphous silicon are prepared by chemical vapor deposition, with each having a thickness of 10-50 nm, such as 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, and 50 nm.

[0115] The present invention also provides a stacked assembly comprising the perovskite solar cell and the crystalline silicon solar cell of the present invention. In the stacked assembly, the perovskite solar cell is disposed above the crystalline silicon solar cell.

[0116] The present invention has the following beneficial effects: 1. The transition layer of the present invention can alleviate stress concentration at the perovskite / electron transport layer interface, reduce grain boundary crack density, and effectively improve photothermal stability.

[0117] 2. This invention utilizes the high conductivity of MXene to form a continuous conductive network at the perovskite / electron transport layer interface, reducing carrier recombination and improving the device fill factor, short-circuit current and photoelectric conversion efficiency.

[0118] 3. The transition layer of the present invention combines the hydrophobicity of fluorinated resin with the chemical stability of MXene, which significantly improves the damp heat stability of perovskite solar cells.

[0119] The present invention will be described below by way of specific embodiments. It should be understood that these embodiments are merely illustrative and are not intended to limit the scope of the invention. The methods, reagents, and materials used in the embodiments and comparative examples are conventional methods, reagents, and materials in the art, unless otherwise stated. The starting material compounds in the embodiments and comparative examples are all commercially available.

[0120] Example 1

[0121] This embodiment describes the fabrication of an inverted tandem perovskite solar cell containing the transition layer of the present invention, comprising the following steps: (1) Polish the N-type silicon wafer to a texture of 300 nm; (2) Intrinsic amorphous silicon on the front side was prepared by chemical vapor deposition. The n-type amorphous silicon had a total thickness of 25 nm. (3) The back side is intrinsic amorphous silicon, p-type amorphous silicon, with a total thickness of 20 nm; (4) A tunneling layer ITO with a thickness of 50 nm was prepared on the surface of n-type amorphous silicon by sputtering. (5) A transparent conductive oxide layer ITO with a thickness of 130 nm was prepared by sputtering. (6) Hole transport layer was prepared by spin coating with solution method, the concentration ratio of 4PACz to MeO-2PACz was 3:1, the total concentration was 1 mg / mL, annealed at 100℃ for 10 min, and the thickness was 3 nm. (7) Prepare a perovskite precursor solution, using FA 0.8 Cs 0.2 Pb(Br 0.2 I 0.8 )3, as the active material of perovskite, perovskite (in the form of Pb) in the perovskite precursor solution 2+ The concentration of DMF was 1.7 mol / mL, the solvent volume ratio was DMF:DMSO=4:1, and phenylethylamine hydroiodide (PEAI) was added to the perovskite precursor solution to regulate crystallization. The concentration of PEAI in the precursor solution was 1 mg / mL. (8) The perovskite layer was prepared by spin coating, with anisole as the antisolvent, and annealed at 100°C for 20 min. The thickness of the perovskite film was 500 nm. (9) First spin-coat Ti3C2T onto the perovskite film. x Chlorobenzene solution of PVDF, Ti3C2T x The mass of Ti3C2T x And 30 wt% of the total mass of PVDF, Ti3C2T x The total concentration of PVDF was 1 mg / mL (spin coating speed 3000 rpm, spin coating time 30 s) to form a high modulus underlayer; then immediately spin coating was performed with Ti3C2T.x Chlorobenzene solution of PVDF, Ti3C2T x The mass of Ti3C2T x And 5 wt% of the total mass of PVDF, Ti3C2T x A low-modulus layer was formed by spin-coating a chlorobenzene solution of PVDF with a total concentration of 1 mg / mL (2000 rpm, 30 s). Then, a three-layer transition layer precursor was obtained by spin-coating a PVDF-chlorobenzene solution with a PVDF concentration of 1.9 mg / mL (1000 rpm, 30 s). Finally, the transition layer precursor was annealed at 100 °C for 10 min to form a transition layer with a thickness of 5 nm. (10) A C60 layer with a thickness of 5 nm was prepared on the surface of the transition layer by thermal evaporation. (11) SnO2 was prepared by atomic layer deposition with a thickness of 20 nm; (12) An IZO layer with a thickness of 50 nm was prepared by sputtering. (13) Preparation of MgF using thermal evaporation method x (Antireflection layer), with a thickness of 110 nm; (14) An Ag metal grid layer (top electrode) with a thickness of 200 nm was prepared by thermal evaporation to complete the battery fabrication.

[0122] Example 2

[0123] The difference from Example 1 lies in implementation step (9), where Ti3C2T is first spin-coated onto the perovskite film. x Chlorobenzene solution of PVDF, Ti3C2T x The mass of Ti3C2T x And 20 wt% of the total mass of PVDF, Ti3C2T x The total concentration of PVDF was 1 mg / mL (spin coating speed 3000 rpm, spin coating time 30 s) to form a high modulus underlayer; then immediately spin coating with Ti3C2T was performed. x Chlorobenzene solution of PVDF, Ti3C2T x The mass of Ti3C2T x And 3 wt% of the total mass of PVDF, Ti3C2T x The total concentration of PVDF was 1 mg / mL (spin coating speed 2000 rpm, spin coating time 30 s) to form a low modulus layer; then a chlorobenzene solution of PVDF with a PVDF concentration of 1.5 mg / mL was spin coated (1000 rpm, 30 s) to obtain a three-layer transition layer precursor; finally, the transition layer precursor was annealed at 100℃ for 10 min to form a transition layer with a thickness of 5 nm.

[0124] Example 3

[0125] The difference from Example 1 lies in implementation step (9), where Ti3C2T is first spin-coated onto the perovskite film. x Chlorobenzene solution of PVDF, Ti3C2T x The mass of Ti3C2T x And 15 wt% of the total mass of PVDF, Ti3C2T x The total concentration of PVDF was 1 mg / mL (spin coating speed 3000 rpm, spin coating time 30 s) to form a high modulus underlayer; then immediately spin coating with Ti3C2T was performed. x Chlorobenzene solution of PVDF, Ti3C2T x The mass of Ti3C2T x And 1 wt% of the total mass of PVDF, Ti3C2T x The total concentration of PVDF was 1 mg / mL (spin coating speed 2000 rpm, spin coating time 30 s) to form a low modulus layer; then a chlorobenzene solution of PVDF with a PVDF concentration of 1 mg / mL was spin coated (1000 rpm, 30 s) to obtain a three-layer transition layer precursor; finally, the transition layer precursor was annealed at 100℃ for 10 min to form a transition layer with a thickness of 5 nm.

[0126] Comparative Example 1

[0127] The difference from Example 1 is that step (9) is not performed, and a C60 layer with a thickness of 10 nm is prepared by direct thermal evaporation on the surface of the perovskite film.

[0128] Comparative Example 2

[0129] The difference from Example 1 is in step (9), where a PVDF chlorobenzene solution is directly spin-coated onto the perovskite film with a PVDF concentration of 1.9 mg / mL (spin-coating speed 1000 rpm, spin-coating time 30 s), and then annealed at 100°C for 10 min to form a transition layer.

[0130] Comparative Example 3

[0131] The difference from Example 1 lies in step (9), where Ti3C2T is first spin-coated onto the perovskite film. x Chlorobenzene solution (spin coating speed 2000 rpm, spin coating time 30 s), Ti3C2T x The mass concentration is 5 wt% (Ti3C2T) x (Percentage of the total mass of the coating solution); then spin-coate a chlorobenzene solution of PVDF with a PVDF concentration of 1.9 mg / mL (1000 rpm, 30 s); finally, anneal the transition layer precursor at 100 °C for 10 min to form the transition layer.

[0132] Comparative Example 4

[0133] The difference from Example 1 lies in step (9), where Ti3C2T is spin-coated onto the perovskite layer. x PVDF in chlorobenzene solution (1000 rpm, 30 s), Ti3C2T x The mass of Ti3C2T x And 30 wt% of the total mass of PVDF, Ti3C2T x The total concentration of PVDF was 1 mg / mL, and the mixture was annealed at 100 °C for 10 min to form a transition layer.

[0134] Comparative Example 5

[0135] The difference from Example 1 lies in step (9), where Ti3C2T is spin-coated onto the perovskite layer. x PVDF in chlorobenzene solution (1000 rpm, 30 s), Ti3C2T x The mass accounts for Ti3C2T x 5 wt% of the total mass of PVDF, Ti3C2T x The total concentration of PVDF was 1 mg / mL, and the mixture was annealed at 100 °C for 10 min to form a transition layer.

[0136] Test case

[0137] Performance testing of perovskite solar devices: At 25°C, using a solar simulator (AM 1.5G standard solar spectrum, incident light power P...) in 100 mW / cm 2 The voltage range was set to 2 V to -0.5 V, and the current output of the perovskite solar cells prepared in Example 1 and Comparative Examples 1-5 was tested at different voltages. The effective cell area was 1.04 cm². 2 The short-circuit current density, open-circuit voltage, fill factor, photoelectric conversion efficiency, and maximum power retention rate after 200 h of high-temperature operation of the perovskite solar cells prepared in Example 1 and Comparative Examples 1-5 were obtained from the characteristic curves.

[0138] (1) Short-circuit current density (J) sc ): The magnitude of the current (J) passing through a unit area of ​​the battery when the voltage across the battery terminals is zero. sc ).

[0139] (2) Open circuit voltage (V) oc : The voltage value corresponding to the current being zero.

[0140] (3) Fill factor (FF): The maximum output power of the battery (P) maxThe ratio of the open-circuit voltage to the product of the short-circuit current is calculated using the formula (P). max / V oc I sc ) 100%, where the maximum power point is the point where the battery output power reaches its maximum value, I sc This is the short-circuit current.

[0141] (4) Photoelectric conversion efficiency (PCE): Photoelectric conversion efficiency refers to the ratio of maximum output power to incident light power (P0). in The ratio of (P) to (P) is calculated using the formula (P) max / P in ) 100%.

[0142] (5) Maximum power (MPP) maintenance rate after 200 h of high temperature operation (85℃ 200 h MPP N2 maintenance): The ratio of the maximum power point of the perovskite solar cell after 200 h of operation at 85℃ to the initial maximum power point. The maximum power point is the point at which the cell output power reaches its maximum value.

[0143] The performance test results of the examples and comparative examples are summarized in Table 1.

[0144] Table 1

[0145] In Examples 1-3, Ti3C2T in the transition layer near the perovskite side x The mass of Ti3C2T x The ratio of the transition layer's modulus to the total mass of PVDF is relatively high, gradually decreasing away from the perovskite side. Therefore, the transition layer near the perovskite side has a higher modulus, while the modulus gradually decreases away from the perovskite side, forming a three-layer gradient structure with gradually decreasing modulus. This alleviates the mechanical stress caused by the abrupt change in modulus between the perovskite and electron transport layer C60 interfaces, resulting in superior MPP stability at high temperatures. In contrast, the transition layers in Comparative Examples 1-5 are single-layer or two modulus gradient layers, with significant modulus differences between them and the perovskite and electron transport layer C60. These layers cannot alleviate mechanical stress and therefore exhibit poor stability.

Claims

1. A transition layer between a perovskite layer and an electron transport layer, characterized in that, The transition layer comprises a fluorinated resin and MXene, with MXene exhibiting a mass concentration gradient distribution along the thickness direction of the transition layer.

2. The transition layer as described in claim 1, characterized in that, The thickness of the transition layer is 2~5 nm.

3. The transition layer as described in claim 1, characterized in that, The MXene is selected from Ti3C2T. x V2CT x Nb2CT x Ti2CT x and Ti3CNT x One or more of them.

4. The transition layer as described in claim 1, characterized in that, The fluorinated resin is selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, and perfluoroalkoxy resins.

5. The transition layer as described in claim 1, characterized in that, The MXene mass concentration on the side of the transition layer closer to the perovskite layer is greater than the MXene mass concentration on the side of the transition layer closer to the electron transport layer.

6. The transition layer as described in claim 1, characterized in that, The transition layer comprises, in the thickness direction, a first fluorinated resin / MXene composite layer to an Nth fluorinated resin / MXene composite layer and an N+1th fluorinated resin layer, or the transition layer comprises, in the thickness direction, a first fluorinated resin / MXene composite layer to an N+1th fluorinated resin / MXene composite layer, where N is an integer ≥2.

7. The transition layer as described in claim 6, characterized in that, The first to the Nth fluorinated resin / MXene composite layers contain fluorinated resin and MXene.

8. The transition layer as described in claim 7, characterized in that, In the first to the Nth fluorinated resin / MXene composite layers, the ratio of the mass of MXene to the total mass of MXene and fluorinated resin is independently 1 to 30 wt%.

9. The transition layer as described in claim 7, characterized in that, In the first fluorinated resin / MXene composite layer, the ratio of the mass of MXene to the total mass of MXene and fluorinated resin is 15~30 wt%.

10. The transition layer as described in claim 7, characterized in that, In the Nth fluorinated resin / MXene composite layer, the ratio of the mass of MXene to the total mass of MXene and fluorinated resin is 1 to 5 wt%.

11. The transition layer as described in claim 6, characterized in that, N is 2.

12. The transition layer as described in claim 6, characterized in that, The N+1th fluorinated resin layer contains fluorinated resin but does not contain MXene.

13. The transition layer as described in claim 6, characterized in that, The N+1th fluorinated resin / MXene composite layer comprises fluorinated resin and MXene, wherein the ratio of the mass of MXene to the total mass of MXene and fluorinated resin in the N+1th fluorinated resin / MXene composite layer is >0 and ≤1 wt%.

14. A method for preparing a transition layer according to any one of claims 1-13, characterized in that, The method includes: (1) Coating the first coating liquid to the Nth coating liquid in sequence, where N is an integer ≥ 2, to obtain a coating precursor containing MXene; the first coating liquid to the Nth coating liquid contain MXene and fluorinated resin; the ratio of the mass of MXene to the total mass of MXene and fluorinated resin in the first coating liquid to the Nth coating liquid decreases in sequence. (2) A resin coating liquid is applied to the surface of the MXene-containing coating precursor to obtain a transition layer precursor, wherein the resin coating liquid contains fluorinated resin and does not contain MXene; or an N+1 coating liquid is applied to the surface of the MXene-containing coating precursor to obtain a transition layer precursor, wherein the N+1 coating liquid contains MXene and fluorinated resin, and the ratio of the mass of MXene in the N+1 coating liquid to the total mass of MXene and fluorinated resin is less than the ratio of the mass of MXene in the N coating liquid to the total mass of MXene and fluorinated resin. (3) Anneal the precursor of the transition layer to obtain the transition layer.

15. The method as described in claim 14, characterized in that, The method has one or more of the following characteristics: The solvents in the first coating liquid to the N+1th coating liquid are independently selected from one or both of isopropanol and chlorobenzene; The ratio of the mass of MXene to the total mass of MXene and fluorinated resin in the first to Nth coating solutions is independently 1 to 30 wt%; The ratio of the mass of MXene in the first coating solution to the total mass of MXene and fluorinated resin is 15~30 wt%. The ratio of the mass of MXene in the Nth coating solution to the total mass of MXene and fluorinated resin is 1~5 wt%. The ratio of the mass of MXene in the (N+1)th coating solution to the total mass of MXene and fluorinated resin is >0 and ≤1 wt%. The total concentration of MXene and fluorinated resin in the first coating solution to the N+1 coating solution is independently 0.5~2 mg / mL; The concentration of fluorinated resin in the resin coating solution is 0.5~1.9 mg / mL; The solvent in the resin coating solution is selected from one or both of chlorobenzene and isopropanol; The annealing temperature is 90℃~120℃, and the annealing time is 10~30 min.

16. The method as described in claim 14, characterized in that, N is 2. The ratio of the mass of MXene in the first coating solution to the total mass of MXene and fluorinated resin is 15~30 wt%, and the ratio of the mass of MXene in the second coating solution to the total mass of MXene and fluorinated resin is 1~5 wt%.

17. The method as described in claim 14, characterized in that, The method has one or more of the following characteristics: The first coating liquid is applied by spin coating, with a spin coating speed of 2000~3000 rpm and a spin coating time of 10~30 s; The second to Nth coating liquids are applied by spin coating, with the spin coating speed independently ranging from 1000 to 2000 rpm and the spin coating time independently ranging from 10 to 30 s. The resin coating liquid is applied by spin coating, with a spin coating speed of 500~1000 rpm and a spin coating time of 10~30 s.

18. A perovskite battery, characterized in that, The perovskite solar cell comprises, in the thickness direction, a hole transport layer, a perovskite layer, a transition layer as described in any one of claims 1-13, and an electron transport layer.

19. The perovskite solar cell as described in claim 18, characterized in that, The electron transport layer is selected from one or more of C60, C70, C60 derivatives, and C70 derivatives.

20. The perovskite solar cell as described in claim 19, characterized in that, The C60 derivative is selected from one or both of [6,6]-phenyl-C61-butyrate isomethyl ester and [6,6]-phenyl-C71-butyrate isomethyl ester.

21. A stacked assembly, characterized in that, The stacked assembly includes a perovskite cell and a crystalline silicon cell as described in any one of claims 18-20, wherein the perovskite cell is disposed above the crystalline silicon cell.

22. The use of the transition layer according to any one of claims 1-13 in a perovskite solar cell, or in relieving stress concentration at the interface between the perovskite layer and the electron transport layer, or in improving the open-circuit voltage, fill factor, short-circuit current, photoelectric conversion efficiency and / or high-temperature operating stability of the perovskite solar cell.

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