Electron transport layer and preparation method thereof, solar cell and preparation method thereof, and photovoltaic module

Abstract

The embodiment of the invention provides an electron transport layer and a preparation method thereof, a solar cell and a preparation method thereof, and a photovoltaic module, and belongs to the technical field of solar cells. A preparation method of an electron transport layer comprises the following steps: placing liquid gallium between an upper substrate and a lower substrate, keeping the temperature of the substrates at 100-200 DEG C, applying a uniaxial vertical pressure of 5kPa-400kPa to the two substrates to carry out extrusion so that the liquid gallium is spread between the upper substrate and the lower substrate, the gallium forms a gallium oxide film on the surface of the substrate through an in-situ oxidation reaction under the air condition, and the electron transport layer is obtained. High-temperature sintering or complex deposition equipment is not needed in the preparation process, the preparation process is simple, the energy consumption is low, the expandability is good, and the method is suitable for efficient preparation and large-scale production of large-area flexible electronic devices; the obtained electron transport layer can improve the electron transport capability, thereby improving the photoelectric conversion efficiency of the solar cell device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cells, in particular to an electron transport layer and a preparation method thereof, a solar cell and a preparation method thereof, and a photovoltaic module. BACKGROUND

[0002] In a perovskite solar cell with an n-i-p structure, titanium dioxide is used as an electron transport material for the electron transport layer (ETL), and the titanium dioxide often needs to be treated at a high temperature to form a high-quality thin film, which is not suitable for a flexible substrate, and the complex steps can also introduce impurities or cause damage to the film layer; in addition, defects are easily formed at the interface between the electron transport layer and the perovskite absorption layer, and these defects will become non-radiative recombination centers, shorten the carrier lifetime, and reduce the photoelectric conversion efficiency; the introduction of lithium ions can effectively improve the conductivity and electron mobility of the titanium dioxide electron transport layer and improve the overall performance of the solar cell device, but lithium ions have strong hygroscopicity and are easy to absorb moisture in a humid environment, which adversely affects the stability of the perovskite layer in the solar cell, and thus reduces the long-term stability and service life of the solar cell device.

[0003] Titanium dioxide thin films prepared by atomic layer deposition (ALD) technology under low-temperature conditions often have many structural defects such as oxygen vacancies and lattice distortions. These defects will cause non-radiative recombination in the electron transport process, reduce the carrier transport efficiency, and also become a source of interface defect states, thereby further reducing the performance of the solar cell device; in recent years, interface engineering strategies have been widely used to optimize the interface contact between the electron transport layer and the perovskite layer, for example, by introducing an ultrathin buffer layer or a surface modifier to reduce the interface energy level mismatch and defect density, thereby improving the device efficiency and stability, but these methods are mostly limited to the surface interface regulation level and are difficult to fundamentally eliminate the interface defect problems caused by the intrinsic characteristics of the material or the process conditions.

[0004] It should be noted that the above content is not necessarily prior art, nor is it used to limit the patent protection scope of the present application. SUMMARY

[0005] The electron transport layer and the preparation method thereof, the solar cell and the preparation method thereof, and the photovoltaic module provided by the embodiments of the present application can solve or alleviate one or more technical problems proposed above.

[0006] The first aspect of the embodiment of the present application provides a preparation method of an electron transport layer, comprising: placing liquid gallium between two substrates, keeping the temperature of the substrates at 100-200 DEG C, and spreading the liquid gallium between the two substrates by applying a uniaxial vertical pressure of 5-400 kPa to the two substrates, and forming a gallium oxide film on the surface of the substrate by in-situ oxidation reaction of the gallium in air to obtain the electron transport layer.

[0007] Optionally, the uniaxial vertical pressure applied to the two substrates is 8-310 kPa.

[0008] Optionally, the extrusion time is 1-5 min.

[0009] Optionally, the method further comprises, after the extrusion, vertically lifting the upper substrate without horizontal sliding.

[0010] Optionally, the thickness of the electron transport layer is 1-50 nm.

[0011] The second aspect of the embodiment of the present application provides an electron transport layer prepared by the preparation method of the electron transport layer.

[0012] Optionally, the electron transport layer is a gallium oxide film, and the thickness of the electron transport layer is 1-50 nm.

[0013] The third aspect of the embodiment of the present application provides a solar cell comprising the electron transport layer prepared by the preparation method of the electron transport layer or the electron transport layer.

[0014] The fourth aspect of the embodiment of the present application provides a preparation method of a solar cell, comprising: providing a substrate; placing liquid gallium between two substrates, keeping the temperature of the substrates at 100-200 DEG C, and spreading the liquid gallium between the two substrates by applying a uniaxial vertical pressure of 5-400 kPa to the two substrates, and forming a gallium oxide film on the surface of the substrate by in-situ oxidation reaction of the gallium in air to obtain the electron transport layer; forming a perovskite layer on the electron transport layer; forming a hole transport layer on the perovskite layer; forming a metal electrode on the hole transport layer.

[0015] The fifth aspect of the embodiment of the present application provides a photovoltaic module comprising the solar cell.

[0016] The technical solution of the embodiment of the present application can have the following advantages: The preparation method provided in the application forms a gallium oxide film on the surface of the substrate as an electron transport layer, which can improve the electron transport capacity and thus improve the photoelectric conversion efficiency of the solar cell device.

[0017] The electron transport layer obtained by the preparation method provided in the application is formed by melting gallium with a low melting point to form liquid gallium and forming a gallium oxide film on the surface of the substrate as an electron transport layer through in-situ oxidation reaction under air conditions. The preparation process does not require high-temperature sintering or complex deposition equipment, and has the advantages of simple preparation process, low energy consumption, good scalability, and suitability for efficient preparation and large-scale production of large-area and flexible electronic devices. BRIEF DESCRIPTION OF DRAWINGS

[0018] In the drawings, like reference numerals designate like or similar parts throughout the several views, and that these drawings should not be construed as limiting of the present disclosure.

[0019] Figure 1 is a schematic diagram of forming a gallium oxide film by placing liquid gallium between the upper and lower substrates provided in the embodiments of the application.

[0020] Figure 2 is a structural schematic diagram of a solar cell provided in the embodiments of the application.

[0021] Figure 3 The SEM images of the perovskite layer surfaces provided in Example 3 and Comparative Example 1 of the application.

[0022] Figure 4 The I-V and QE curve results of the perovskite solar cell test provided in Example 3 and Comparative Example 1 of the application.

[0023] Figure 5 The normalized photoelectric conversion efficiency test results of the perovskite solar cell provided in Example 3 and Comparative Example 1 under normal temperature and atmospheric environment.

[0024] BRIEF DESCRIPTION OF DRAWINGS Figure 2 In the drawings, like reference numerals designate like or similar parts throughout the several views, and that these drawings should not be construed as limiting of the present disclosure.

[0025] Figure 3 The SEM images of the perovskite layer surfaces provided in Example 3 and Comparative Example 1 of the application. Figure 3 The SEM images of the perovskite layer surfaces provided in Example 3 and Comparative Example 1 of the application.

[0026] Figure 4 The I-V test results provided in Example 3 and Comparative Example 1 of the application. Figure 4The middle-right graph is the QE test result. DETAILED DESCRIPTION

[0027] Embodiments of the present application are described in detail below with reference to examples illustrated in the accompanying drawings. In the drawings, the size and relative sizes of layers, regions, elements, and the like can be exaggerated for clarity. Like reference numerals can represent like elements throughout the drawings. The embodiments described below are examples of the present application and are not intended to limit the present application. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict if possible.

[0028] It should be understood that when an element or layer is referred to as being "on", "adjacent", "connected to", or "coupled to" another element or layer, it can be directly on, adjacent, connected or coupled to the other element or layer, or intervening elements or layers can be present. In contrast, when an element is referred to as being "directly on", "directly adjacent", "directly connected to", or "directly coupled to" another element or layer, then there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. can be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present application. Similarly, a second element, component, region, layer or section discussed below could be termed a first element, component, region, layer or section without departing from the teachings of the present application.

[0029] In the present application, unless specifically defined otherwise, the terms "mounting", "connected", "connecting", "fixed", and the like, should be understood broadly, for example, can be fixedly connected, or detachably connected, or integrated; can be mechanically connected, or electrically connected; can be directly connected, or indirectly connected through an intermediate medium; can be the internal communication of two elements, or the interaction relationship of two elements, unless specifically defined otherwise. For those skilled in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0030] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0031] In this application, when numerical intervals (i.e., numerical ranges) are involved, unless otherwise specified, the distribution of selectable numerical values ​​within the numerical interval is considered continuous, and includes the two endpoints of the numerical interval (i.e., the minimum and maximum values), as well as every numerical value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that numerical interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include percentage intervals, ratio intervals, proportion intervals, etc.

[0032] This application provides a method for fabricating an electron transport layer, comprising: placing liquid gallium between two substrates, the temperature of which is maintained at 100℃-200℃; applying a uniaxial vertical pressure of 5kPa-400kPa to the two substrates to spread the liquid gallium between them; and forming a gallium oxide film on the substrate surface through an in-situ oxidation reaction under air conditions, thereby obtaining the electron transport layer. Based on this, the fabrication method provided in this application forms a gallium oxide film on the substrate surface as an electron transport layer, which can improve electron transport capability and thus improve the photoelectric conversion efficiency of solar cell devices. Furthermore, the electron transport layer obtained by the fabrication method provided in this application uses gallium with a low melting point to form a gallium oxide film on the substrate surface through an in-situ oxidation reaction using liquid imprinting. The fabrication process does not require high-temperature sintering or complex deposition equipment, is simple in process, has low energy consumption, and possesses good scalability, making it suitable for the efficient fabrication and large-scale production of large-area, flexible electronic devices.

[0033] Exemplary embodiments according to this application will now be described in more detail. It should be understood that these exemplary embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein.

[0034] This application provides a method for fabricating an electron transport layer. Liquid gallium is placed between two substrates, the temperature of which is maintained at 100℃-200℃. The liquid gallium is spread between the two substrates by applying a uniaxial vertical pressure of 5kPa-400kPa. Gallium oxide is then formed on the substrate surface through an in-situ oxidation reaction under air conditions. A film is formed to obtain an electron transport layer; the thickness of the electron transport layer is 1~50nm.

[0035] In an optional embodiment, the substrate is a flexible substrate, and the flexible substrate is made of at least one of polyimide (PI), polyester (PET), polyethylene naphthalate (PEN) or metal foil, and a flexible solar cell is prepared by using a flexible substrate.

[0036] In an optional embodiment, the substrate is a bottom cell substrate, which includes at least one of crystalline silicon bottom cells (crystalline silicon solar cells), CIGS thin-film solar cells, cadmium telluride thin-film solar cells, III-V thin-film solar cells, or perovskite solar cells.

[0037] In an optional embodiment, the substrate is a conductive substrate, which is a structure in which a transparent conductive layer is formed on a substrate, and the substrate is a glass substrate; the transparent conductive material used for the transparent conductive layer includes, but is not limited to, at least one of ITO, IZO, IWO, FTO, ICO, AZO, ATO or GZO; the method for preparing the conductive substrate includes, but is not limited to, depositing the transparent conductive material on the glass substrate by magnetron sputtering (PVD) or reactive plasma deposition (RPD) to obtain the conductive substrate and the transparent conductive layer, and the thickness of the transparent conductive layer is 20nm~200nm.

[0038] In optional embodiments, the substrate includes, but is not limited to, at least one of ITO conductive glass, IZO conductive glass, IWO conductive glass, FTO conductive glass, ICO conductive glass, AZO conductive glass, ATO conductive glass or GZO conductive glass.

[0039] In the embodiments of the present application, gallium with a low melting point (melting point of 29.76℃) is used, liquid gallium is placed between the upper and lower substrates and spread, and uniaxial vertical pressure is applied to the two substrates for extrusion, and the gallium forms a gallium oxide film on the substrate surface through in-situ oxidation reaction under air conditions; by applying uniaxial vertical pressure to the substrate for extrusion, the liquid gallium can be uniformly spread between the upper and lower substrates, and a gallium oxide film with uniform thickness can also be obtained, especially the in-situ generation of the gallium oxide film induced by the oxidation reaction of gallium on the substrate surface; the gallium oxide film obtained by the present application as an electron transport layer is beneficial to the efficient extraction of photo-generated carriers, and significantly improves the photoelectric conversion efficiency and response speed of the solar cell; the gallium oxide film obtained by the present application has good chemical stability and thermal stability, and shows smaller performance decay in long-term light and humidity tests, and improves the service life of the solar cell device.

[0040] In optional embodiments, the uniaxial vertical pressure applied to the two substrates includes, but is not limited to, 5kPa, 8kPa, 10kPa, 15kPa, 18kPa, 20kPa, 25kPa, 28kPa, 30kPa, 35kPa, 38kPa, 40kPa, 45kPa, 50kPa, 55kPa, 60kPa, 65kPa, 70kPa, 75kPa, 80kPa, 85kPa, 90kPa, 95kPa, 100kPa, 110kPa, 120kPa, 128kPa, 135kPa, 140kPa, 150kPa, 160kPa, 170kPa, 180kPa, 190kPa, 200kPa, 210kPa, 220kPa, 230kPa, 240kPa, 250kPa, 260kPa, 270kPa, 280kPa, 290kPa, 300kPa, 310kPa, 320kPa, 330kPa, 340kPa, 350kPa, 360kPa, 370kPa, 380kPa, 390kPa, 400kPa.

[0041] In optional embodiments, the uniaxial vertical pressure applied to the two substrates for extrusion is 8kPa-310kPa.

[0042] In the embodiments of the present application, the uniaxial vertical pressure applied to the two substrates is 5kPa-400kPa, preferably 8kPa-310kPa. The uniaxial vertical pressure can improve the spreading and film forming properties of liquid gallium on the substrate, and can fully oxidize the gallium to obtain a high-quality gallium oxide film. The gallium oxide film formed has excellent interface compatibility, which can avoid the presence of bubbles or gaps at the interface between the perovskite layer and the gallium oxide film, and can improve the performance of the perovskite solar cell. If the uniaxial vertical pressure applied to the two substrates is too small, the obtained electron transport layer is thick, which reduces the performance of the perovskite solar cell. The possible reason is that the small extrusion pressure cannot make the gallium spread evenly between the upper and lower substrates, and the liquid gallium cannot fully form gallium oxide on the surface of the substrate through in-situ oxidation reaction. When the perovskite layer is subsequently obtained on the electron transport layer, there are bubbles or gaps between the interface of the electron transport layer and the perovskite layer, which reduces the electron transport efficiency and thus reduces the performance of the perovskite solar cell. If the uniaxial vertical pressure applied to the two substrates is too large, the obtained electron transport layer cannot improve the performance of the perovskite solar cell, but rather reduces the photoelectric conversion efficiency of the perovskite solar cell. The possible reason is that the large uniaxial vertical pressure easily causes damage to the substrate, thereby reducing the photoelectric conversion efficiency of the perovskite solar cell.

[0043] In optional embodiments, the temperature of the substrate is, but not limited to, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃.

[0044] In optional embodiments, the temperature of the substrate is 150℃.

[0045] In optional embodiments, the extrusion time is 1min-5min.

[0046] In optional embodiments, the extrusion time is, but not limited to, 1min, 2min, 3min, 4min, 5min.

[0047] In optional embodiments, the method further comprises, after the extrusion is completed, the upper substrate is lifted vertically without horizontal sliding, the upper and lower substrates form a gallium oxide film, and an electron transport layer is obtained. The thickness of the electron transport layer is 1-50nm.

[0048] The thickness of the electron transport layer includes, but is not limited to, 1 nm, 1.5 nm, 2 nm, 2.6 nm, 3 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 15 nm, 18 nm, 20 nm, 23 nm, 25 nm, 28 nm, 30 nm, 33 nm, 35 nm, 38 nm, 40 nm, 42 nm, 45 nm, 48 nm, or 50 nm.

[0049] The electronic transport layer is prepared by the method for preparing an electronic transport layer as described above.

[0050] In an optional embodiment, the electronic transport layer is a gallium oxide film, and the thickness of the electronic transport layer is 1-50 nm.

[0051] The solar cell includes the electronic transport layer prepared by the method for preparing an electronic transport layer as described above or the electronic transport layer as described above.

[0052] In an optional embodiment, the solar cell includes, in sequence, a substrate, an electronic transport layer, a perovskite layer, a hole transport layer, and a metal electrode, wherein the electronic transport layer is a gallium oxide film.

[0053] In an optional embodiment, the substrate is a conductive substrate, which is a structure in which a transparent conductive layer is formed on a substrate substrate, and the substrate substrate is a glass substrate. The transparent conductive material used in the transparent conductive layer includes, but is not limited to, at least one of ITO, IZO, IWO, FTO, ICO, AZO, ATO, or GZO. The method for preparing the conductive substrate includes, but is not limited to, depositing the transparent conductive material on the glass substrate by magnetron sputtering (PVD) or reactive plasma deposition (RPD) to obtain the conductive substrate and obtain the transparent conductive layer, and the thickness of the transparent conductive layer is 20-200 nm.

[0054] In an optional embodiment, the substrate includes, but is not limited to, at least one of ITO conductive glass, IZO conductive glass, IWO conductive glass, FTO conductive glass, ICO conductive glass, AZO conductive glass, ATO conductive glass, or GZO conductive glass.

[0055] In an optional embodiment, the material structure of the perovskite layer has a general formula of ; wherein A is a cation, which is usually a monovalent cation with a large ionic radius, such as methylamine ion ( ), dimethylamine ion ( ), formamidinium ion ( ), ethylammonium ion ( ), cesium ion ( one or more of rubidium ions (Rb ), or guanidinium ions (Gua ). The B is a cation, typically a divalent metal cation such as one or more of lead ions (Pb ), tin ions (Sn ), or germanium ions (Ge ); the X is an anion, including halide anions such as one or more of bromide ions (Br ), iodide ions (I ), chloride ions (Cl ), and thiocyanate ions (SCN ), tetrafluoroborate ions (BF4 ), hexafluorophosphate ions (PF6 ).

[0056] In optional embodiments, the perovskite layer employs a material including but not limited to , or .

[0057] In embodiments of the present application, the perovskite thin film is formed by spin coating on a gallium oxide film. By forming the perovskite thin film on the gallium oxide film, the perovskite thin film grains can be more uniform, the grain size is more consistent as a whole, and the grains are more tightly bound, which helps to reduce the recombination of carriers and further improves the photoelectric conversion efficiency of the solar cell.

[0058] In optional embodiments, the hole transport layer employs a material including but not limited to a transition metal oxide, an organic small molecule material, or a polymer.

[0059] The transition metal oxide includes but is not limited to nickel oxide (NiO) or copper oxide (CuO).

[0060] The polymer includes but is not limited to poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS).

[0061] The organic small molecule material is generally referred to as SAM (self-assembled monolayer) material, and the SAM material includes but is not limited to one or more of the following: [2-(9H-carbazol-9-yl)ethyl] phosphonic acid (2PACz), [2-(3,6-diphenyl-9H-carbazol-9-yl) ethyl] phosphonic acid (Me-2PACz), (2-(3,6-dimethoxy-9H-carbazol-9-yl) ethyl) phosphonic acid (MeO-2PACz), 2-(3,6-dibromo-9H-carbazol-9-yl) ethyl] phosphonic acid (Br-2PACz), 2-(3,6-dichloro-9H-carbazol-9-yl) ethyl] phosphonic acid (Cl-2PACz), 2-(3,6-difluoro-9H-carbazol-9-yl) ethyl] phosphonic acid (F-2PACz), [4-(9H-carbazol-9-yl) ethyl] phosphonic acid (4PACz), [4-(3,6-dimethyl-9H-carbazol-9-yl) butyl] phosphonic acid (Me-4PACz), [4-(3,6-dimethoxy-9H-carbazol-9-yl) butyl] phosphonic acid (MeO-4PACz), [4-(3,6-dibromo-9H-carbazol-9-yl) butyl] phosphonic acid (2Br-4PACz), (4-(3,6-dichloro-9H-carbazol-9-yl) butyl) phosphonic acid (2Cl-4PACz), (4-(3,6-difluoro-9H-carbazol-9-yl) butyl) phosphonic acid (2F-4PACz), [4-(7H-dibenzo carbazol-7-yl) butyl] phosphonic acid (4PADCB), [4-(2,7-dibromo-9,9-dimethylacridin-10(9H)-yl) butyl] phosphonic acid (2Br-4DMAcPA), 4-phenyl butyric acid sodium salt (4-PBA), (2-(4-(bis(4-methoxyphenyl)amino)phenyl)-1-cyanovinyl) phosphonic acid (MPA-CPA), or [2-(3,7-dibromo-10H-phenothiazin-10-yl) ethyl] phosphonic acid (Br-2EPT).

[0062] In optional embodiments, the material employed by the hole transport layer includes one or more of Spiro-OMeTAD, PTAA, P3HT, Spiro-TTB, F4-TCNQ, , CuSCN, , , CdS or CdSe.

[0063] In optional embodiments, the metal electrode includes but is not limited to a gold electrode, a silver electrode, an aluminum electrode, a copper electrode, the metal electrode is prepared in a manner including but not limited to evaporation, thermal evaporation, screen printing, electroplating, laser technology, PVD (Physical Vapor Deposition) or inkjet printing, and the thickness of the metal electrode is 10 nm to 20 μm.

[0064] In an optional embodiment, the surface of the metal electrode is provided with an anti-reflection layer.

[0065] Embodiments of the present application provide a method for preparing a solar cell, comprising: providing a substrate; placing liquid gallium between the upper and lower substrates, the temperature of the substrates being maintained at 100-200°C, and extruding the liquid gallium between the upper and lower substrates by applying a uniaxial vertical pressure of 5-400kPa to the substrates, so that the gallium spreads between the upper and lower substrates, and a gallium oxide film is formed on the surface of the substrate by in-situ oxidation of the gallium in air, to obtain an electron transport layer; forming a perovskite layer on the electron transport layer; forming a hole transport layer on the perovskite layer; forming a metal electrode on the hole transport layer.

[0066] In an optional embodiment, the method for preparing a perovskite solar cell comprises: using FTO glass or ITO glass as the substrate; placing liquid gallium between the upper and lower substrates, the temperature of the substrates being maintained at 100-200°C, and extruding the liquid gallium between the upper and lower substrates by applying a uniaxial vertical pressure of 5-400kPa to the substrates, so that the gallium spreads between the upper and lower substrates, and a gallium oxide film is formed on the surface of the substrate by in-situ oxidation of the gallium in air, to obtain an electron transport layer; spin-coating or evaporating a layer of perovskite material on the surface of the electron transport layer to form a perovskite layer; spin-coating a hole transport layer material on the surface of the perovskite layer to obtain a hole transport layer; vacuum evaporating or magnetron sputtering gold, silver, aluminum or copper on the hole transport layer as a metal electrode.

[0067] In an optional embodiment, the method for preparing a perovskite solar cell comprises: S1. Preparing the substrate: cutting indium tin oxide (ITO) conductive glass into appropriate size, and ultrasonically cleaning in deionized water, acetone and isopropanol for 8-20min (for example 8min, 10min, 12min, 14min, 16min, 18min, 20min) in sequence, to remove impurities and organic contaminants adsorbed on the surface of the ITO conductive glass; then blowing dry with nitrogen, and irradiating in a ultraviolet ozone treatment instrument for 15-30min (for example 15min, 18min, 20min, 22min, 24min, 26min, 28min, 30min), to further improve the surface energy of the substrate and enhance the adhesion of the subsequent thin film.

[0068] S2. Preparation of an electron transport layer: using a pipette to take 100 μL-500 μL of a droplet of liquid gallium with a purity of 99.99% and drop it on the ITO conductive glass surface pretreated in the above S1 step and preheated to 150 C of the ITO conductive glass surface; the droplet of liquid gallium is dropped on the ITO conductive glass surface pretreated in the above S1 step and preheated to C of the ITO conductive glass surface; another piece of ITO conductive glass, which is also pretreated in the above S1 step and preheated to C of the ITO conductive glass, is vertically pressed on the droplet of liquid gallium, and the temperature of the two pieces of ITO conductive glass is continuously maintained at C, and a uniaxial vertical pressure of 5 kPa-400 kPa is applied to the two pieces of ITO conductive glass to extrude for 1 min-5 min, so that the liquid gallium spreads between the two pieces of ITO conductive glass, and the gallium forms a gallium oxide film on the surface of the substrate through in-situ oxidation reaction under air conditions; after the extrusion is completed, the upper piece of ITO conductive glass is smoothly and vertically lifted without horizontal sliding, and a gallium oxide film is obtained on the surfaces of the upper and lower pieces of ITO conductive glass as an electron transport layer, and the thickness of the electron transport layer is 1-50 nm.

[0069] In the embodiments of the present application, part of the liquid gallium will overflow the ITO conductive glass during the extrusion process due to the influence of the pressure, and the overflowed part will be subsequently cleaned off without affecting the gallium oxide film obtained on the surface of the ITO conductive glass.

[0070] In optional embodiments, a uniaxial vertical pressure of 8 kPa-310 kPa is applied to the two pieces of ITO conductive glass to extrude.

[0071] S3. Preparation of a perovskite layer: a solution of with a concentration of 1 mol / L-2 mol / L (for example, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L) is obtained by dissolving the solution in a mixed solvent of DMF (N,N-dimethylformamide) and DMSO (dimethyl sulfoxide) (the volume ratio of DMF to DMSO is 8:1, 9:1, 10:1); 50 μL-100 μL (for example, 50 μL, 60 μL, 70 μL, 80 μL, 90 μL, 100 μL) is spin-coated on the electron transport layer obtained on the surface of the ITO conductive glass in the S2 step, and after the spin coating is completed, the ITO conductive glass is moved to a hot stage at 60°C-80°C (for example, 60°C, 70°C, 80°C) to anneal for 0.5 min-2 min (for example, 0.5 min, 1 min, 1.5 min, 2 min) to obtain thin film, the spin-coating speed is 1000 rpm-2000 rpm (for example, 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm, 2000 rpm), the spin-coating time is 20 s-40 s (for example, 20 s, 35 s, 30 s, 35 s, 40 s); then 100 μL-150 μL (for example, 100 μL, 110 μL, 120 μL, 130 μL, 140 μL, 150 μL) of the cation solution is spin-coated on the obtained thin film after annealing thin film, the spin-coating speed is 1500 rpm-2500 rpm (for example, 1500 rpm, 1800 rpm, 2000 rpm, 2200 rpm, 2500 rpm), the spin-coating time is 20 s-40 s (for example, 20 s, 35 s, 30 s, 35 s, 40 s), and the ITO conductive glass is placed on a 130℃-180℃ (for example, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃) flat plate hot stage for annealing for 10 min-20 min (for example, 10 min, 12 min, 15 min, 18 min, 20 min) to form a perovskite thin film with a thickness of 900 nm-1000 nm as a perovskite layer, and then cooled to room temperature for standby, and the above entire process is carried out in a nitrogen environment.

[0072] The cation solution is obtained by dissolving formamidinium iodide (FAI), methylamine bromide (MABr) and methylamine chloride (MACI) in isopropyl alcohol (IPA), the mass concentration of formamidinium iodide in the cation solution is 80-100 mg / mL (for example, 80 mg / mL, 85 mg / mL, 90 mg / mL, 95 mg / mL, 100 mg / mL), the mass concentration of methylamine bromide is 5-8 mg / mL (for example, 5 mg / mL, 5.5 mg / mL, 6 mg / mL, 6.4 mg / mL, 7 mg / mL, 7.5 mg / mL, 8 mg / mL), and the mass concentration of methylamine chloride is 8-10 mg / mL (for example, 8 mg / mL, 8.5 mg / mL, 9 mg / mL, 9.5 mg / mL, 10 mg / mL).

[0073] S4. Preparation of the hole transport layer: Weigh 70-78 mg (e.g., 70 mg, 70.5 mg, 71 mg, 71.5 mg, 72 mg, 72.5 mg, 73 mg, 73.5 mg, 74 mg, 74.5 mg, 75.5 mg, 76 mg, 76.5 mg, 77 mg, 77.5 mg, 78 mg) of Spiro-OMeTAD (2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene) and dissolve it in 0.5 mL-2 mL (e.g., 0.5 mL) of water. Add 0.8 mL, 1 mL, 1.2 mL, 1.5 mL, 1.8 mL, or 2 mL of chlorobenzene and stir for at least 3 hours. Then add 26 μL-33 μL (e.g., 26 μL, 27 μL, 28 μL, 29 μL, 30 μL, 31 μL, 32 μL, or 33 μL) of tributyl phosphate (tBP) and 15-20 μL (e.g., 15 μL, 15.5 μL, 16 μL, 16.5 μL, 17 μL, 17.8 μL, 18 μL, 18.5 μL, 19 μL, 19.5 μL, or 20 μL) of a 500 mg / L solution. A lithium salt solution with concentrations ranging from mg / mL to 600 mg / mL (e.g., 500 mg / mL, 510 mg / mL, 520 mg / mL, 530 mg / mL, 540 mg / mL, 550 mg / mL, 560 mg / mL, 570 mg / mL, 580 mg / mL, 590 mg / mL, 600 mg / mL) was prepared and stirred for at least 1 hour. The solution was then filtered through a filter membrane to obtain a Spiro-OMeTAD solution. 60 μL of the Spiro-OMeTAD solution was then added dropwise to the surface of the perovskite film obtained in step S3 for spin-coating. The film is prepared by setting the spin coating speed to 2500-3500 rpm (e.g., 2500 rpm, 2800 rpm, 3000 rpm, 2300 rpm, 3500 rpm) and the spin coating time to 20s-40s (e.g., 20s, 35s, 30s, 35s, 40s). After spin coating, the ITO conductive glass is placed in a light-proof electronic dehumidifier for at least 24 hours to ensure that Spiro-OMeTAD is fully oxidized to obtain an oxide film. The oxide film serves as a hole transport layer, and the thickness of the hole transport layer is 120nm-200nm.

[0074] S5. Preparation of metal electrodes: Weigh 0.1-0.5g (e.g., 0.1g, 0.2g, 0.3g, 0.4g, 0.5g) of metal (e.g., gold or silver) and place it in a tungsten boat. Fix the ITO conductive glass with hole transport layer obtained in S4 in the sample chamber of the vapor deposition machine and deposit a metal layer on the hole transport layer to obtain a metal electrode with a thickness of 80nm-100nm.

[0075] In an optional embodiment, after closing the vapor deposition machine door, the mechanical pump and the fore-stage valve are turned on sequentially, and the molecular pump is started when the gas pressure drops below 2 Pa; the sample chamber gas pressure of the vapor deposition machine is then reduced to... Afterward, turn on the evaporation power supply and evaporation rotation function, and adjust the evaporation source current to control the evaporation rate within the range of 1.5–2 Å / s. When the film thickness gauge shows 1000 Å, turn off the evaporation power supply and evaporation rotation device in sequence, then turn off the molecular pump and the fore-stage valve, and finally turn off the mechanical pump. Open the vent valve and remove the ITO conductive glass coated with metal.

[0076] This application provides a photovoltaic module, including the solar cell described above.

[0077] In an optional embodiment, the photovoltaic module includes at least one battery string, which includes at least two solar cells as described above.

[0078] The following sections will describe the electron transport layer and its preparation method, the structure and fabrication method of the solar cell, and related comparative examples provided in this application, along with relevant performance tests.

[0079] Exemplary embodiments according to this application will now be described in more detail with reference to the accompanying drawings. It should be understood that these exemplary embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein.

[0080] Example 1 A perovskite solar cell, such as Figure 2 As shown, it includes: a substrate 101, an electron transport layer 102, a perovskite layer 103, a hole transport layer 104, and a metal electrode 105, which are stacked sequentially.

[0081] A method for fabricating a perovskite solar cell is as follows: S1. Pretreatment of substrate: Indium tin oxide (ITO) conductive glass with a size of 20mm×20mm was ultrasonically cleaned in deionized water, acetone and isopropanol for 10min each; then dried with nitrogen and irradiated in an ultraviolet ozone treatment instrument for 20min; the indium tin oxide (ITO) conductive glass has a structure in which an ITO transparent conductive layer is formed on the glass substrate, and the thickness of the ITO transparent conductive layer is 150 nm.

[0082] S2. Preparation of the electron transport layer: Using a pipette, drop 400 μL of 99.99% pure liquid gallium into the pretreatment layer from step S1 above and preheat it to [temperature missing]. The surface of the ITO conductive glass; another piece of glass that has undergone the same pretreatment step S1 and is preheated to... The ITO conductive glass is vertically pressed on the liquid gallium droplet, the two pieces of ITO conductive glass keep relative position, and the temperature of the two pieces of ITO conductive glass is kept at 8kPa uniaxial vertical pressure for 3min, so that the liquid gallium is uniformly spread into a film between the two pieces of ITO conductive glass, and the gallium forms a gallium oxide film on the surface of the substrate by in-situ oxidation reaction under air condition; after the extrusion is completed, the upper piece of ITO conductive glass is vertically lifted smoothly without horizontal sliding, and a gallium oxide film is obtained on the surface of the upper and lower pieces of ITO conductive glass as an electron transport layer, and the thickness of the electron transport layer is 50nm.

[0083] S3. Preparation of perovskite layer: 70μL solution is dissolved in a mixed solvent of DMF (N, N-dimethylformamide) and DMSO (dimethyl sulfoxide) (the volume ratio of DMF and DMSO is 9:1) to obtain a solution with a concentration of 1.5mol / L; 70μL solution is spin-coated on the electron transport layer obtained on the surface of the ITO conductive glass in the S2 step, the spin-coating speed is 1500rpm, the spin-coating time is 30s, and after the spin-coating is completed, the ITO conductive glass is moved to a hot stage at 70℃ for annealing for 1min to obtain a thin film; then 120μL of the cation solution is spin-coated on the thin film obtained after annealing, the spin-coating speed is 2000rpm, the spin-coating time is 30s, and after the spin-coating is completed, the ITO conductive glass is placed on a hot stage at 150 for annealing for 15min to form a perovskite thin film with a thickness of 900nm-1000nm as a perovskite layer, and the whole process is carried out in a nitrogen environment.

[0084] The cation solution is obtained by dissolving formamidinium iodide (FAI), methylamine bromide (MABr) and methylamine chloride (MACl) in isopropyl alcohol (IPA), and the mass concentration of formamidinium iodide in the cation solution is 90mg / mL, the mass concentration of methylamine bromide is 6.4mg / mL, and the mass concentration of methylamine chloride is 9mg / mL.

[0085] S4. Preparation of hole transport layer: 74.5 mg of Spiro-OMeTAD (2,2',7,7'-tetra[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene) was dissolved in 1 mL of chlorobenzene and stirred for 3 hours, then 29 μL of tributyl phosphate (tBP) and 17.8 μL of a lithium bis-trifluoromethanesulfonimide solution with a concentration of 520 mg / mL were added, and the stirring was continued for 1 hour, the solvent of the lithium bis-trifluoromethanesulfonimide solution was acetonitrile, and the Spiro-OMeTAD solution was obtained by filtering through a filter membrane with a pore size of 0.22 microns; 60 μL of the Spiro-OMeTAD solution was added dropwise to the perovskite film surface obtained in S3 to form a film by spin coating, the spin coating speed was set to 3000 rpm, and the spin coating time was 30 s, after the spin coating was completed, the ITO conductive glass was placed in a light-proof electronic moisture-proof cabinet for at least 24 hours to ensure that the Spiro-OMeTAD was fully oxidized to obtain an oxidized film, which served as a hole transport layer, and the thickness of the hole transport layer was 120-200 nm.

[0086] S5. Preparation of metal electrode: 0.3 g (for example, 0.1 g, 0.2 g, 0.3 g, 0.4 g, 0.5 g) of gold was placed in a tungsten boat, and the ITO conductive glass with a hole transport layer obtained in S4 was fixed in the sample chamber of the evaporation machine to perform evaporation on the hole transport layer to obtain gold as a metal electrode, and the thickness of the metal electrode was 80-100 nm.

[0087] The process of placing liquid gallium between the upper and lower two substrates to form a gallium oxide film provided in this embodiment can refer to Figure 1 the provided schematic diagram.

[0088] Example 2 The perovskite solar cell of Example 2 was prepared according to the preparation method of Example 1, except that in S2, a uniaxial vertical pressure of 28 kPa was applied to the two pieces of ITO conductive glass for extrusion.

[0089] Specifically, the preparation method of the electron transport layer is: 400 μL of a droplet of liquid gallium with a purity of 99.99% was taken using a pipette and dropped onto the surface of the ITO conductive glass pre-processed and pre-heated to in the above S1 step; the other piece of ITO conductive glass also pre-processed and pre-heated to in the above S1 step was vertically pressed on the liquid gallium droplet, and the two pieces of ITO conductive glass maintained a relative position, and the temperature of the two pieces of ITO conductive glass was maintained at and a uniaxial vertical pressure of 28 kPa is applied to the two pieces of ITO conductive glass to extrude for 3 min, so that the liquid gallium is uniformly spread into a film between the two pieces of ITO conductive glass, and the gallium forms a gallium oxide film on the surface of the substrate through in-situ oxidation reaction under air condition; after the extrusion is completed, the upper piece of ITO conductive glass is smoothly and vertically lifted, and there is no horizontal sliding during the vertical lifting, and a gallium oxide film is obtained on the surfaces of the upper and lower pieces of ITO conductive glass as an electron transport layer, and the thickness of the electron transport layer is 13 nm.

[0090] Example 3 The perovskite solar cell of Example 3 is prepared according to the preparation method of Example 1, except that in the S2 step: a uniaxial vertical pressure of 128 kPa is applied to the two pieces of ITO conductive glass to extrude.

[0091] Specifically, the preparation method of the electron transport layer is as follows: A droplet of 400 μL of liquid gallium with a purity of 99.99% is taken using a pipette and dropped on the surface of the ITO conductive glass which has been pretreated and preheated to 200 °C according to the S1 step described above; another piece of ITO conductive glass which has also been pretreated and preheated to 200 °C according to the S1 step described above is vertically pressed on the droplet of liquid gallium, and the two pieces of ITO conductive glass are kept in position, and the temperature of the two pieces of ITO conductive glass is continuously kept at 200 °C, and a uniaxial vertical pressure of 128 kPa is applied to the two pieces of ITO conductive glass to extrude for 3 min, so that the liquid gallium is uniformly spread into a film between the two pieces of ITO conductive glass, and the gallium forms a gallium oxide film on the surface of the substrate through in-situ oxidation reaction under air condition; after the extrusion is completed, the upper piece of ITO conductive glass is smoothly and vertically lifted, and there is no horizontal sliding during the vertical lifting, and a gallium oxide film is obtained on the surfaces of the upper and lower pieces of ITO conductive glass as an electron transport layer, and the thickness of the electron transport layer is 2.6 nm. Example 4 The perovskite solar cell of Example 4 is prepared according to the preparation method of Example 1, except that in the S2 step: a uniaxial vertical pressure of 310 kPa is applied to the two pieces of ITO conductive glass to extrude.

[0092] Specifically, the preparation method of the electron transport layer is as follows: A droplet of 400 μL of liquid gallium with a purity of 99.99% is taken using a pipette and dropped on the surface of the ITO conductive glass which has been pretreated and preheated to 200 °C according to the S1 step described above; another piece of ITO conductive glass which has also been pretreated and preheated to 200 °C according to the S1 step described above is vertically pressed on the droplet of liquid gallium, and the two pieces of ITO conductive glass are kept in position, and the temperature of the two pieces of ITO conductive glass is continuously kept at 200 °C,

[0093] and a uniaxial vertical pressure of 310 kPa is applied to the two pieces of ITO conductive glass to extrude for 3 min, so that the liquid gallium is uniformly spread into a film between the two pieces of ITO conductive glass, and the gallium forms a gallium oxide film on the surface of the substrate through in-situ oxidation reaction under air condition; after the extrusion is completed, the upper piece of ITO conductive glass is smoothly and vertically lifted, and there is no horizontal sliding during the vertical lifting, and a gallium oxide film is obtained on the surfaces of the upper and lower pieces of ITO conductive glass as an electron transport layer, and the thickness of the electron transport layer is 2.6 nm. ​​The ITO conductive glass is vertically pressed on the liquid gallium droplet, the two pieces of ITO conductive glass keep relative position, and the temperature of the two pieces of ITO conductive glass is kept at 150°C. Then, 310 kPa of uniaxial vertical pressure is applied to the two pieces of ITO conductive glass for extrusion for 3 min, so that the liquid gallium is uniformly spread into a film between the two pieces of ITO conductive glass, and the gallium forms a gallium oxide film on the surface of the substrate by in-situ oxidation reaction under air condition; after the extrusion is completed, the upper piece of ITO conductive glass is vertically lifted smoothly without horizontal sliding, and a gallium oxide film is obtained on the surface of the upper and lower pieces of ITO conductive glass as an electron transport layer, and the thickness of the electron transport layer is 1 nm.

[0094] Comparative Example 1 The perovskite solar cell of Comparative Example 1 is prepared by referring to the preparation method of Example 1, except that in the S2 step, the preparation method of the electron transport layer is as follows: 90 μL of titanium dioxide precursor solution is taken, and is dropped on the ITO conductive glass pretreated in the S1 step for spin coating into a film, the spin coating speed is 4200 rpm, the spin coating time is 30 s, and after the spin coating is completed, the ITO conductive glass is placed in a muffle furnace for calcination at 500°C for 30 min to obtain a titanium dioxide film as an electron transport layer; and the thickness of the electron transport layer is 12 nm.

[0095] The preparation method of the titanium dioxide precursor solution is as follows: 20 mL of tetrabutyl titanate is slowly dropped into 150 mL of anhydrous ethanol, the magnetic stirring is continuously performed during the dropping process, and after standing for half an hour, an A solution is obtained; 8 mL of ethylene glycol amine is dropped into 30 mL of anhydrous ethanol, and 2 mL of pure water is further added for mixing to obtain a B solution; the B solution is slowly dropped into the continuously stirred A solution, the dropping time of the B solution lasts at least two hours, and after the dropping is completed, the titanium dioxide precursor solution is stored in a dark and dry environment for 3 days.

[0096] Comparative Example 2 The perovskite solar cell of Comparative Example 2 is prepared by referring to the preparation method of Example 1, except that in the S2 step, 2 kPa of uniaxial vertical pressure is applied to the two pieces of ITO conductive glass for extrusion.

[0097] Specifically, the preparation method of the electron transport layer is as follows: 400 μL of liquid gallium droplet with a purity of 99.99% is taken by using a pipette and is dropped on the surface of the ITO conductive glass pretreated in the above S1 step and preheated to 150°C; and another piece of ITO conductive glass which is also pretreated in the above S1 step and preheated to 150°C is used as a substrate. ​​Two ITO conductive glass sheets are vertically pressed onto a liquid gallium droplet, maintaining their relative positions and keeping the temperature of the two ITO conductive glass sheets constant. A uniaxial vertical pressure of 2 kPa is applied to two ITO conductive glass sheets and squeezed for 3 minutes to allow liquid gallium to spread uniformly between the two ITO conductive glass sheets into a film. The gallium forms a gallium oxide film on the substrate surface through an in-situ oxidation reaction under air conditions. After squeezing, the upper ITO conductive glass sheet is lifted vertically and smoothly without lateral slippage during the vertical lifting process. Gallium oxide films are obtained on the surfaces of the upper and lower ITO conductive glass sheets as electron transport layers, and the thickness of the electron transport layer is 220 nm.

[0098] Comparative Example 3 The perovskite solar cell of Comparative Example 3 was prepared according to the preparation method of Example 1, except that in step S2: a uniaxial vertical pressure of 500 kPa was applied to two ITO conductive glass sheets for extrusion.

[0099] Specifically, the method for preparing the electron transport layer is as follows: Using a pipette, drop 400 μL of 99.99% pure liquid gallium into the pretreatment step S1 above and preheat it to [temperature missing]. The surface of the ITO conductive glass; another piece of glass that has undergone the same pretreatment step S1 and is preheated to... Two ITO conductive glass sheets are vertically pressed onto a liquid gallium droplet, maintaining their relative positions and keeping the temperature of the two ITO conductive glass sheets constant. A uniaxial vertical pressure of 500 kPa is applied to two ITO conductive glass sheets and squeezed for 3 minutes to allow liquid gallium to spread uniformly between the two ITO conductive glass sheets into a film. The gallium forms a gallium oxide film on the substrate surface through an in-situ oxidation reaction under air conditions. After squeezing, the upper ITO conductive glass sheet is lifted vertically and smoothly without lateral slippage during the vertical lifting process. Gallium oxide films are obtained on the surfaces of the upper and lower ITO conductive glass sheets as electron transport layers, and the thickness of the electron transport layer is 0.59 nm.

[0100] Performance testing: The perovskite layers obtained in Example 3 and Comparative Example 1 were observed using a scanning electron microscope (SEM), and the corresponding SEM images were obtained (see...). Figure 3 ); Figure 3 The rightmost image in the middle section is a SEM image of the perovskite layer surface provided in Example 3; Figure 3 The image on the left in the middle is a SEM image of the perovskite layer surface provided in Comparative Example 1.

[0101] pass Figure 3The provided perovskite layer surface SEM image can be seen that the perovskite film grain size formed by Comparative Example 1 is relatively uneven, there are some larger size grains and smaller size grains, and the interface between the grains is relatively more; while the perovskite film grain of Example 3 is more uniform, the grain size is overall more consistent, and the grains are more closely combined, and the compactness of the film is relatively better.

[0102] Comparing Comparative Example 1 and Example 3, the perovskite film provided by Example 3 is formed by spin coating on the gallium oxide film. By forming a perovskite film on the gallium oxide film, the perovskite film grains in the perovskite film can be more uniform, the grain size is overall more consistent, and the grains are more closely combined, which helps to reduce the recombination of carriers and further improve the photoelectric conversion efficiency of the solar cell.

[0103] The performance of the perovskite solar cells provided by Examples 1-4 and Comparative Examples 1-3 was tested, and the photoelectric conversion efficiency, open circuit voltage, short circuit current density, and fill factor of the corresponding perovskite solar cells were obtained, as shown in Table 1 and Figure 4

[0104] The fill factor (FF) used herein refers to the ratio of the actual maximum obtainable power (Pm or Vmp x Jmp) to the theoretical (non-actual obtainable) power (Jsc x Voc). Therefore, FF can be determined by the following formula: FF = (Vmp x Jmp) / (Jsc x Voc), where Jmp and Vmp represent the current density and voltage at the maximum power point (Pm), respectively, which is obtained by changing the resistance in the circuit until J x V is maximum; Jsc and Voc represent the short circuit current and open circuit voltage, respectively. The fill factor is a key parameter for evaluating solar cells. Commercial solar cells usually have a fill factor of about 60% and above.

[0105] The open circuit voltage (Voc) used herein is the potential difference between the anode and the cathode of the device under the condition of no external load connection.

[0106] The short circuit current (Isc) used herein is the maximum current flowing through the photovoltaic cell or module output when short-circuited (voltage V = 0) under STC conditions.

[0107] The power conversion efficiency (PCE) of the solar cell used herein refers to the percentage of power converted from absorbed light to electrical energy. The power conversion efficiency (PCE) of the solar cell can be calculated by the standard test conditions (STC) incident light radiation (E: ) and the surface area of the solar cell ( ). STC usually refers to the conditions of temperature 25°C, radiation intensity 100​ , the spectrum of air mass 1.5 (AM1.5).

[0108] The performance test results of the perovskite solar cells provided in Examples 1-4 and Comparative Examples 1-3 are embodied in Table 1.

[0109] Table 1

[0110] As can be seen from Table 1 above, the perovskite solar cells provided in Examples 1-4 are extruded by applying a uniaxial vertical pressure of 5 kPa-400 kPa, preferably 8 kPa-310 kPa, to the ITO conductive glass, so that the liquid gallium is evenly spread between the two pieces of ITO conductive glass, and the gallium forms a gallium oxide film on the surface of the ITO conductive glass as an electron transport layer through in-situ oxidation reaction, which can improve the performance of the perovskite solar cell, the open-circuit voltage is increased to 1.121-1.150 V, the fill factor is increased to 79.1-82.1%, and the photoelectric conversion efficiency is increased to 22.1-23.6%. The gallium oxide film obtained in the application as an electron transport layer can improve the electron mobility, more efficiently extract and transport photo-generated electrons, and reduce interface recombination loss. Compared with Comparative Example 1 which uses a titanium dioxide film as an electron transport layer, the gallium oxide film formed on the surface of the ITO conductive glass as an electron transport layer by in-situ oxidation reaction of gallium in the application can improve the photoelectric conversion efficiency of the perovskite solar cell, and the cost of obtaining the gallium oxide film is low, which exhibits more excellent performance in the perovskite solar cell, and provides a new technical path for the development of low-cost oxides as electron transport materials.

[0111] Comparing Example 1 and Comparative Example 2, in Comparative Example 2, the ITO conductive glass is extruded by applying a uniaxial vertical pressure of 2 kPa, and the extrusion pressure used in Comparative Example 2 is less than the uniaxial vertical pressure of 8 kPa used in Example 1, and the obtained electron transport layer cannot improve the performance of the perovskite solar cell, but rather reduces the performance of the perovskite solar cell. The possible reason is that the extrusion pressure is small, the obtained electron transport layer is thick, and the gallium cannot form gallium oxide on the surface of the ITO conductive glass through in-situ oxidation reaction, so that when the perovskite layer is obtained on the electron transport layer subsequently, there are bubbles or gaps between the electron transport layer and the perovskite layer, which leads to a decrease in electron transport efficiency, thereby reducing the performance of the perovskite solar cell.

[0112] Comparing Example 1 and Comparative Example 3, in Comparative Example 3, a uniaxial vertical pressure of 500 kPa is applied to the ITO conductive glass for extrusion, and the extrusion pressure used in Comparative Example 3 is large, and the electron transport layer obtained cannot improve the performance of the perovskite solar cell, but rather reduces the photoelectric conversion efficiency of the perovskite solar cell. The possible reason is that the uniaxial vertical pressure used is too large, causing damage to the substrate, thereby reducing the photoelectric conversion efficiency of the perovskite solar cell.

[0113] By Figure 4 As can be seen from the I-V curve in the left graph, the current density of the perovskite solar cell provided in Example 3 decreases relatively more slowly in the high voltage region, and the overall current density level is relatively better than that of Comparative Example 1. The perovskite solar cell provided in Example 3 has a higher short-circuit current or fill factor, and has good photoelectric conversion efficiency at different voltages. By Figure 4 As can be seen from the QE curve in the right graph, the external quantum efficiency of the perovskite solar cell provided in Example 3 exhibits better response capability in a wider wavelength range compared with Comparative Example 1, and the integral current density test results also reflect that the perovskite solar cell provided in Example 3 can collect more photo-generated carriers and has higher light utilization efficiency, which helps to improve the overall photoelectric performance of the solar cell.

[0114] Comparing Comparative Example 1 and Example 3, the perovskite solar cell provided in Example 3 uses a gallium oxide film as an electron transport layer, and is better than Comparative Example 1 in terms of current output of photoelectric conversion and response efficiency to different wavelengths of light.

[0115] The perovskite solar cells provided in Example 3 and Comparative Example 1 were tested for normalized photoelectric conversion efficiency in a normal temperature and atmospheric environment, and the test results are shown in Figure 5 .

[0116] By Figure 5 It can be seen that the perovskite solar cell prepared in Example 3 has good stability, and the photoelectric conversion efficiency decreases at a small rate with time, and can be maintained at a high level within 600 h, indicating that its photoelectric conversion performance is more stable and has better anti-degradation capability than the solar cell provided in Comparative Example 1. The solar cell provided in Example 3 has more advantages in long-term use scenarios.

[0117] The embodiments of the present application can also provide a photovoltaic module (not shown), which includes a perovskite solar cell as described above. The photovoltaic module includes at least one cell string, and the cell string includes at least two perovskite solar cells as described above.

[0118] It should be noted that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like merely are used to facilitate the description of the application and are not intended to limit or restrict the scope of the application to the terms so used. The terms "inner", "outer" refer to the inner and outer with respect to the contour of each component itself. For example, if the device in the drawings is inverted, the device described as "above" or "above" other devices or configurations will be positioned "below" or "below" other devices or configurations. Thus, the exemplary term "above" can include both "above" and "below" orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used herein are interpreted accordingly.

[0119] It should also be noted that the "one embodiment", "another embodiment", "embodiment", and the like in the present application refer to the specific features, structures or characteristics described in connection with the embodiment, which are included in at least one embodiment described in the general description of the present application. The same expression appearing in several places in the specification does not necessarily refer to the same embodiment. Further, when a specific feature, structure or characteristic is described in connection with any embodiment, it is claimed that the implementation of such feature, structure or characteristic in connection with other embodiments also falls within the scope of the present application.

[0120] In the above embodiments, the description of each embodiment has its own emphasis, and the parts not described in detail in a certain embodiment can be referred to the relevant description of other embodiments.

[0121] It should also be noted that the above is only the preferred embodiment of the present application, and does not limit the patent protection scope of the present application, and any equivalent structure or equivalent process transformation using the content of the present application specification and drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for preparing an electron transport layer, characterized in that, include: Liquid gallium is placed between two substrates, the temperature of which is maintained at 100℃-200℃. The liquid gallium is spread between the two substrates by applying a uniaxial vertical pressure of 5kPa-400kPa. The gallium forms a gallium oxide film on the surface of the substrates through an in-situ oxidation reaction under air conditions, thus obtaining an electron transport layer.

2. The method for preparing an electron transport layer according to claim 1, characterized in that, The two substrates are subjected to uniaxial vertical pressure of 8kPa-310kPa for compression.

3. The method for preparing an electron transport layer according to claim 1, characterized in that, The extrusion time is 1 min to 5 min.

4. The method for preparing an electron transport layer according to claim 1, characterized in that, The method further includes lifting the upper substrate vertically without lateral sliding after the extrusion is completed.

5. The method for preparing an electron transport layer according to any one of claims 1-4, characterized in that, The thickness of the electron transport layer is 1~50nm.

6. An electron transport layer, characterized in that, It is prepared by the method for preparing the electron transport layer as described in any one of claims 1 to 5.

7. The electron transport layer according to claim 6, characterized in that, The electron transport layer is a gallium oxide film, and the thickness of the electron transport layer is 1~50nm.

8. A solar cell, characterized in that, This includes the electron transport layer prepared by the method described in any one of claims 1 to 5, or the electron transport layer described in claim 6.

9. A method for preparing a solar cell, characterized in that, include: Provide a base; Liquid gallium is placed between two substrates, the temperature of which is maintained at 100℃-200℃. Liquid gallium is spread between the two substrates by applying a uniaxial vertical pressure of 5kPa-400kPa. The gallium forms a gallium oxide film on the surface of the substrates through an in-situ oxidation reaction under air conditions, thus obtaining an electron transport layer. A perovskite layer is formed on the electron transport layer; A hole transport layer is formed on the perovskite layer; Metal electrodes are formed on the hole transport layer.

10. A photovoltaic cell module, characterized in that, This includes solar cells prepared by the method described in claim 8 or claim 9.

Images